From: Davidlohr Bueso <dave@stgolabs.net>
Add basic plumbing for memory expander devices that support Back
Invalidation. This introduces a 'hdm-db=on|off' parameter and
exposes the relevant BI RT/Decoder component cachemem registers.
Some noteworthy properties:
- Devices require enabling Flit mode across the CXL topology.
- Explicit BI-ID commit is required.
- HDM decoder support both host and dev coherency models.
Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
v6: Initialize type variable to avoid a false compiler warning
from some versions of gcc. (Michael Tsirkin)
---
docs/system/devices/cxl.rst | 23 +++++
include/hw/cxl/cxl_component.h | 54 ++++++++++-
include/hw/cxl/cxl_device.h | 3 +
hw/cxl/cxl-component-utils.c | 142 ++++++++++++++++++++++++++--
hw/mem/cxl_type3.c | 9 +-
hw/pci-bridge/cxl_downstream.c | 2 +-
hw/pci-bridge/cxl_root_port.c | 3 +-
hw/pci-bridge/cxl_upstream.c | 2 +-
hw/pci-bridge/pci_expander_bridge.c | 2 +-
9 files changed, 225 insertions(+), 15 deletions(-)
diff --git a/docs/system/devices/cxl.rst b/docs/system/devices/cxl.rst
index ca15a0da1c1d..9d0771cdfd73 100644
--- a/docs/system/devices/cxl.rst
+++ b/docs/system/devices/cxl.rst
@@ -384,6 +384,29 @@ An example of 4 devices below a switch suitable for 1, 2 or 4 way interleave::
-device cxl-type3,bus=swport3,persistent-memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem3,sn=0x4 \
-M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
+An example of 4 type3 devices with volatile memory below a switch. Two of the devices
+use HDM-DB for coherence, which requires operating in Flit mode::
+
+ qemu-system-x86_64 -M q35,cxl=on -m 4G,maxmem=8G,slots=8 -smp 4 \
+ ...
+ -object memory-backend-ram,id=cxl-mem0,share=on,size=256M \
+ -object memory-backend-ram,id=cxl-mem1,share=on,size=256M \
+ -object memory-backend-ram,id=cxl-mem2,share=on,size=256M \
+ -object memory-backend-ram,id=cxl-mem3,share=on,size=256M \
+ -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
+ -device cxl-rp,port=0,bus=cxl.1,id=root_port0,chassis=0,slot=0 \
+ -device cxl-rp,port=1,bus=cxl.1,id=root_port1,chassis=0,slot=1 \
+ -device cxl-upstream,bus=root_port0,id=us0,x-256b-flit=on \
+ -device cxl-downstream,port=0,bus=us0,id=swport0,chassis=0,slot=4 \
+ -device cxl-type3,bus=swport0,volatile-memdev=cxl-mem0,id=cxl-mem0,sn=0x1,x-256b-flit=on,hdm-db=on \
+ -device cxl-downstream,port=1,bus=us0,id=swport1,chassis=0,slot=5 \
+ -device cxl-type3,bus=swport1,volatile-memdev=cxl-mem1,id=cxl-mem1,sn=0x2,x-256b-flit=on,hdm-db=on \
+ -device cxl-downstream,port=2,bus=us0,id=swport2,chassis=0,slot=6 \
+ -device cxl-type3,bus=swport2,volatile-memdev=cxl-mem2,id=cxl-mem2,sn=0x3 \
+ -device cxl-downstream,port=3,bus=us0,id=swport3,chassis=0,slot=7 \
+ -device cxl-type3,bus=swport3,volatile-memdev=cxl-mem3,id=cxl-mem3,sn=0x4 \
+ -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
+
A simple arm/virt example featuring a single direct connected CXL Type 3
Volatile Memory device::
diff --git a/include/hw/cxl/cxl_component.h b/include/hw/cxl/cxl_component.h
index 1f167d3ef79b..ffc82202206c 100644
--- a/include/hw/cxl/cxl_component.h
+++ b/include/hw/cxl/cxl_component.h
@@ -67,6 +67,8 @@ CXLx_CAPABILITY_HEADER(LINK, 2)
CXLx_CAPABILITY_HEADER(HDM, 3)
CXLx_CAPABILITY_HEADER(EXTSEC, 4)
CXLx_CAPABILITY_HEADER(SNOOP, 5)
+CXLx_CAPABILITY_HEADER(BI_RT, 6)
+CXLx_CAPABILITY_HEADER(BI_DECODER, 7)
/*
* Capability structures contain the actual registers that the CXL component
@@ -211,10 +213,55 @@ HDM_DECODER_INIT(3);
(CXL_IDE_REGISTERS_OFFSET + CXL_IDE_REGISTERS_SIZE)
#define CXL_SNOOP_REGISTERS_SIZE 0x8
-QEMU_BUILD_BUG_MSG((CXL_SNOOP_REGISTERS_OFFSET +
- CXL_SNOOP_REGISTERS_SIZE) >= 0x1000,
+#define CXL_BI_RT_CAP_VERSION 1
+#define CXL_BI_RT_REGISTERS_OFFSET \
+ (CXL_SNOOP_REGISTERS_OFFSET + CXL_SNOOP_REGISTERS_SIZE)
+#define CXL_BI_RT_REGISTERS_SIZE 0xC
+
+REG32(CXL_BI_RT_CAPABILITY, CXL_BI_RT_REGISTERS_OFFSET)
+ FIELD(CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 0, 1)
+REG32(CXL_BI_RT_CTRL, CXL_BI_RT_REGISTERS_OFFSET + 0x4)
+ FIELD(CXL_BI_RT_CTRL, COMMIT, 0, 1)
+REG32(CXL_BI_RT_STATUS, CXL_BI_RT_REGISTERS_OFFSET + 0x8)
+ FIELD(CXL_BI_RT_STATUS, COMMITTED, 0, 1)
+ FIELD(CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 1, 1)
+ FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 8, 4)
+ FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 12, 4)
+
+/* CXL r3.2 8.2.4.27 - CXL BI Decoder Capability Structure */
+#define CXL_BI_DECODER_CAP_VERSION 1
+#define CXL_BI_DECODER_REGISTERS_OFFSET \
+ (CXL_BI_RT_REGISTERS_OFFSET + CXL_BI_RT_REGISTERS_SIZE)
+#define CXL_BI_DECODER_REGISTERS_SIZE 0xC
+
+REG32(CXL_BI_DECODER_CAPABILITY, CXL_BI_DECODER_REGISTERS_OFFSET)
+ FIELD(CXL_BI_DECODER_CAPABILITY, HDM_D, 0, 1)
+ FIELD(CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT, 1, 1)
+REG32(CXL_BI_DECODER_CTRL, CXL_BI_DECODER_REGISTERS_OFFSET + 0x4)
+ FIELD(CXL_BI_DECODER_CTRL, BI_FW, 0, 1)
+ FIELD(CXL_BI_DECODER_CTRL, BI_ENABLE, 1, 1)
+ FIELD(CXL_BI_DECODER_CTRL, COMMIT, 2, 1)
+REG32(CXL_BI_DECODER_STATUS, CXL_BI_DECODER_REGISTERS_OFFSET + 0x8)
+ FIELD(CXL_BI_DECODER_STATUS, COMMITTED, 0, 1)
+ FIELD(CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 1, 1)
+ FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 8, 4)
+ FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 12, 4)
+
+QEMU_BUILD_BUG_MSG((CXL_BI_DECODER_REGISTERS_OFFSET +
+ CXL_BI_DECODER_REGISTERS_SIZE) >= 0x1000,
"No space for registers");
+/* track BI explicit commit handling for route table and decoder */
+enum {
+ CXL_BISTATE_RT = 0,
+ CXL_BISTATE_DECODER,
+ CXL_BISTATE_MAX
+};
+
+typedef struct bi_state {
+ uint64_t last_commit; /* last 0->1 transition */
+} BIState;
+
typedef struct component_registers {
/*
* Main memory region to be registered with QEMU core.
@@ -259,6 +306,7 @@ typedef struct cxl_component {
};
CDATObject cdat;
+ BIState bi_state[CXL_BISTATE_MAX];
} CXLComponentState;
void cxl_component_register_block_init(Object *obj,
@@ -266,7 +314,7 @@ void cxl_component_register_block_init(Object *obj,
const char *type);
void cxl_component_register_init_common(uint32_t *reg_state,
uint32_t *write_msk,
- enum reg_type type);
+ enum reg_type type, bool bi);
void cxl_component_create_dvsec(CXLComponentState *cxl_cstate,
enum reg_type cxl_dev_type, uint16_t length,
diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
index 7d9236db8c85..393f3122173b 100644
--- a/include/hw/cxl/cxl_device.h
+++ b/include/hw/cxl/cxl_device.h
@@ -770,6 +770,9 @@ struct CXLType3Dev {
CXLMemSparingReadAttrs rank_sparing_attrs;
CXLMemSparingWriteAttrs rank_sparing_wr_attrs;
+ /* BI flows */
+ bool hdmdb;
+
struct dynamic_capacity {
HostMemoryBackend *host_dc;
AddressSpace host_dc_as;
diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
index 91770f103a85..a7d36e1128c2 100644
--- a/hw/cxl/cxl-component-utils.c
+++ b/hw/cxl/cxl-component-utils.c
@@ -71,10 +71,40 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
case 4:
if (cregs->special_ops && cregs->special_ops->read) {
return cregs->special_ops->read(cxl_cstate, offset, 4);
- } else {
- QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
- return cregs->cache_mem_registers[offset / 4];
}
+
+ QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
+
+ if (offset == A_CXL_BI_RT_STATUS ||
+ offset == A_CXL_BI_DECODER_STATUS) {
+ int type;
+ uint64_t started;
+
+ type = (offset == A_CXL_BI_RT_STATUS) ?
+ CXL_BISTATE_RT : CXL_BISTATE_DECODER;
+ started = cxl_cstate->bi_state[type].last_commit;
+
+ if (started) {
+ uint32_t *cache_mem = cregs->cache_mem_registers;
+ uint32_t val = cache_mem[offset / 4];
+ uint64_t now;
+ int set;
+
+ now = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
+ /* arbitrary 100 ms to do the commit */
+ set = !!(now >= started + 100);
+
+ if (offset == A_CXL_BI_RT_STATUS) {
+ val = FIELD_DP32(val, CXL_BI_RT_STATUS, COMMITTED, set);
+ } else {
+ val = FIELD_DP32(val, CXL_BI_DECODER_STATUS, COMMITTED,
+ set);
+ }
+ stl_le_p((uint8_t *)cache_mem + offset, val);
+ }
+ }
+
+ return cregs->cache_mem_registers[offset / 4];
case 8:
qemu_log_mask(LOG_UNIMP,
"CXL 8 byte cache mem registers not implemented\n");
@@ -118,6 +148,47 @@ static void dumb_hdm_handler(CXLComponentState *cxl_cstate, hwaddr offset,
stl_le_p((uint8_t *)cache_mem + offset, value);
}
+static void bi_handler(CXLComponentState *cxl_cstate, hwaddr offset,
+ uint32_t value)
+{
+ ComponentRegisters *cregs = &cxl_cstate->crb;
+ uint32_t sts, *cache_mem = cregs->cache_mem_registers;
+ bool to_commit = false;
+ int type = 0; /* Unused value - work around for compiler warning */
+
+ switch (offset) {
+ case A_CXL_BI_RT_CTRL:
+ to_commit = FIELD_EX32(value, CXL_BI_RT_CTRL, COMMIT);
+ if (to_commit) {
+ sts = cxl_cache_mem_read_reg(cxl_cstate,
+ R_CXL_BI_RT_STATUS, 4);
+ sts = FIELD_DP32(sts, CXL_BI_RT_STATUS, COMMITTED, 0);
+ stl_le_p((uint8_t *)cache_mem + R_CXL_BI_RT_STATUS, sts);
+ type = CXL_BISTATE_RT;
+ }
+ break;
+ case A_CXL_BI_DECODER_CTRL:
+ to_commit = FIELD_EX32(value, CXL_BI_DECODER_CTRL, COMMIT);
+ if (to_commit) {
+ sts = cxl_cache_mem_read_reg(cxl_cstate,
+ R_CXL_BI_DECODER_STATUS, 4);
+ sts = FIELD_DP32(sts, CXL_BI_DECODER_STATUS, COMMITTED, 0);
+ stl_le_p((uint8_t *)cache_mem + R_CXL_BI_DECODER_STATUS, sts);
+ type = CXL_BISTATE_DECODER;
+ }
+ break;
+ default:
+ break;
+ }
+
+ if (to_commit) {
+ cxl_cstate->bi_state[type].last_commit =
+ qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
+ }
+
+ stl_le_p((uint8_t *)cache_mem + offset, value);
+}
+
static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
unsigned size)
{
@@ -141,6 +212,9 @@ static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
if (offset >= A_CXL_HDM_DECODER_CAPABILITY &&
offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) {
dumb_hdm_handler(cxl_cstate, offset, value);
+ } else if (offset == A_CXL_BI_RT_CTRL ||
+ offset == A_CXL_BI_DECODER_CTRL) {
+ bi_handler(cxl_cstate, offset, value);
} else {
cregs->cache_mem_registers[offset / 4] = value;
}
@@ -230,7 +304,7 @@ static void ras_init_common(uint32_t *reg_state, uint32_t *write_msk)
}
static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
- enum reg_type type)
+ enum reg_type type, bool bi)
{
int decoder_count = CXL_HDM_DECODER_COUNT;
int hdm_inc = R_CXL_HDM_DECODER1_BASE_LO - R_CXL_HDM_DECODER0_BASE_LO;
@@ -255,7 +329,9 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
UIO_DECODER_COUNT, 0);
ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, MEMDATA_NXM_CAP, 0);
ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY,
- SUPPORTED_COHERENCY_MODEL, 0); /* Unknown */
+ SUPPORTED_COHERENCY_MODEL,
+ /* host+dev or Unknown */
+ type == CXL2_TYPE3_DEVICE && bi ? 3 : 0);
ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_GLOBAL_CONTROL,
HDM_DECODER_ENABLE, 0);
write_msk[R_CXL_HDM_DECODER_GLOBAL_CONTROL] = 0x3;
@@ -278,9 +354,43 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
}
}
+static void bi_rt_init_common(uint32_t *reg_state, uint32_t *write_msk)
+{
+ /* switch usp must commit the new BI-ID, timeout of 2secs */
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 1);
+
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CTRL, COMMIT, 0);
+ write_msk[R_CXL_BI_RT_CTRL] = 0x1;
+
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMITTED, 0);
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 0);
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 0x6);
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 0x2);
+}
+
+static void bi_decoder_init_common(uint32_t *reg_state, uint32_t *write_msk,
+ enum reg_type type)
+{
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, HDM_D, 0);
+ /* switch dsp must commit the new BI-ID, timeout of 2secs */
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT,
+ (type != CXL2_ROOT_PORT && type != CXL2_TYPE3_DEVICE));
+
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_FW, 0);
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_ENABLE, 0);
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, COMMIT, 0);
+ write_msk[R_CXL_BI_DECODER_CTRL] = 0x7;
+
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMITTED, 0);
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 0);
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 0x6);
+ ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 0x2);
+}
+
void cxl_component_register_init_common(uint32_t *reg_state,
uint32_t *write_msk,
- enum reg_type type)
+ enum reg_type type,
+ bool bi)
{
int caps = 0;
@@ -320,7 +430,7 @@ void cxl_component_register_init_common(uint32_t *reg_state,
case CXL2_LOGICAL_DEVICE:
/* + HDM */
init_cap_reg(HDM, 5, 1);
- hdm_init_common(reg_state, write_msk, type);
+ hdm_init_common(reg_state, write_msk, type, bi);
/* fallthrough */
case CXL2_DOWNSTREAM_PORT:
case CXL2_DEVICE:
@@ -335,6 +445,24 @@ void cxl_component_register_init_common(uint32_t *reg_state,
abort();
}
+ /* back invalidate */
+ if (bi) {
+ switch (type) {
+ case CXL2_UPSTREAM_PORT:
+ init_cap_reg(BI_RT, 11, CXL_BI_RT_CAP_VERSION);
+ bi_rt_init_common(reg_state, write_msk);
+ break;
+ case CXL2_ROOT_PORT:
+ case CXL2_DOWNSTREAM_PORT:
+ case CXL2_TYPE3_DEVICE:
+ init_cap_reg(BI_DECODER, 12, CXL_BI_DECODER_CAP_VERSION);
+ bi_decoder_init_common(reg_state, write_msk, type);
+ break;
+ default:
+ break;
+ }
+ }
+
ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, ARRAY_SIZE, caps);
#undef init_cap_reg
}
diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
index 3c7ecd8c48bc..3f09c589ae58 100644
--- a/hw/mem/cxl_type3.c
+++ b/hw/mem/cxl_type3.c
@@ -748,6 +748,11 @@ static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
return false;
}
+ if (!ct3d->flitmode && ct3d->hdmdb) {
+ error_setg(errp, "hdm-db requires operating in 256b flit");
+ return false;
+ }
+
if (ct3d->hostvmem) {
MemoryRegion *vmr;
char *v_name;
@@ -1317,7 +1322,8 @@ static void ct3d_reset(DeviceState *dev)
pcie_cap_fill_link_ep_usp(PCI_DEVICE(dev), ct3d->width, ct3d->speed,
ct3d->flitmode);
- cxl_component_register_init_common(reg_state, write_msk, CXL2_TYPE3_DEVICE);
+ cxl_component_register_init_common(reg_state, write_msk,
+ CXL2_TYPE3_DEVICE, ct3d->hdmdb);
cxl_device_register_init_t3(ct3d, CXL_T3_MSIX_MBOX);
/*
@@ -1356,6 +1362,7 @@ static const Property ct3_props[] = {
DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLType3Dev,
width, PCIE_LINK_WIDTH_16),
DEFINE_PROP_BOOL("x-256b-flit", CXLType3Dev, flitmode, false),
+ DEFINE_PROP_BOOL("hdm-db", CXLType3Dev, hdmdb, false),
};
static uint64_t get_lsa_size(CXLType3Dev *ct3d)
diff --git a/hw/pci-bridge/cxl_downstream.c b/hw/pci-bridge/cxl_downstream.c
index 64086d8ec2f2..320818a8f1ce 100644
--- a/hw/pci-bridge/cxl_downstream.c
+++ b/hw/pci-bridge/cxl_downstream.c
@@ -39,7 +39,7 @@ static void latch_registers(CXLDownstreamPort *dsp)
uint32_t *write_msk = dsp->cxl_cstate.crb.cache_mem_regs_write_mask;
cxl_component_register_init_common(reg_state, write_msk,
- CXL2_DOWNSTREAM_PORT);
+ CXL2_DOWNSTREAM_PORT, true);
}
/* TODO: Look at sharing this code across all CXL port types */
diff --git a/hw/pci-bridge/cxl_root_port.c b/hw/pci-bridge/cxl_root_port.c
index 5641048084a4..e2093ac39ee6 100644
--- a/hw/pci-bridge/cxl_root_port.c
+++ b/hw/pci-bridge/cxl_root_port.c
@@ -101,7 +101,8 @@ static void latch_registers(CXLRootPort *crp)
uint32_t *reg_state = crp->cxl_cstate.crb.cache_mem_registers;
uint32_t *write_msk = crp->cxl_cstate.crb.cache_mem_regs_write_mask;
- cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT);
+ cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT,
+ true);
}
static void build_dvsecs(PCIDevice *d, CXLComponentState *cxl)
diff --git a/hw/pci-bridge/cxl_upstream.c b/hw/pci-bridge/cxl_upstream.c
index c352d11dc7b7..fb8d19539c9f 100644
--- a/hw/pci-bridge/cxl_upstream.c
+++ b/hw/pci-bridge/cxl_upstream.c
@@ -90,7 +90,7 @@ static void latch_registers(CXLUpstreamPort *usp)
uint32_t *write_msk = usp->cxl_cstate.crb.cache_mem_regs_write_mask;
cxl_component_register_init_common(reg_state, write_msk,
- CXL2_UPSTREAM_PORT);
+ CXL2_UPSTREAM_PORT, usp->flitmode);
ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, TARGET_COUNT, 8);
}
diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
index b6e2eb796951..11623a5666f6 100644
--- a/hw/pci-bridge/pci_expander_bridge.c
+++ b/hw/pci-bridge/pci_expander_bridge.c
@@ -300,7 +300,7 @@ static void pxb_cxl_dev_reset(DeviceState *dev)
uint32_t *write_msk = cxl_cstate->crb.cache_mem_regs_write_mask;
int dsp_count = 0;
- cxl_component_register_init_common(reg_state, write_msk, CXL2_RC);
+ cxl_component_register_init_common(reg_state, write_msk, CXL2_RC, false);
/*
* The CXL specification allows for host bridges with no HDM decoders
* if they only have a single root port.
--
2.51.0On Wed, Feb 04, 2026 at 12:12:14PM +0000, Jonathan Cameron wrote:
> From: Davidlohr Bueso <dave@stgolabs.net>
>
> Add basic plumbing for memory expander devices that support Back
> Invalidation. This introduces a 'hdm-db=on|off' parameter and
> exposes the relevant BI RT/Decoder component cachemem registers.
>
> Some noteworthy properties:
> - Devices require enabling Flit mode across the CXL topology.
> - Explicit BI-ID commit is required.
> - HDM decoder support both host and dev coherency models.
>
> Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
> Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
more troubles:
https://gitlab.com/mstredhat/qemu/-/jobs/12984846000
> ---
> v6: Initialize type variable to avoid a false compiler warning
> from some versions of gcc. (Michael Tsirkin)
> ---
> docs/system/devices/cxl.rst | 23 +++++
> include/hw/cxl/cxl_component.h | 54 ++++++++++-
> include/hw/cxl/cxl_device.h | 3 +
> hw/cxl/cxl-component-utils.c | 142 ++++++++++++++++++++++++++--
> hw/mem/cxl_type3.c | 9 +-
> hw/pci-bridge/cxl_downstream.c | 2 +-
> hw/pci-bridge/cxl_root_port.c | 3 +-
> hw/pci-bridge/cxl_upstream.c | 2 +-
> hw/pci-bridge/pci_expander_bridge.c | 2 +-
> 9 files changed, 225 insertions(+), 15 deletions(-)
>
> diff --git a/docs/system/devices/cxl.rst b/docs/system/devices/cxl.rst
> index ca15a0da1c1d..9d0771cdfd73 100644
> --- a/docs/system/devices/cxl.rst
> +++ b/docs/system/devices/cxl.rst
> @@ -384,6 +384,29 @@ An example of 4 devices below a switch suitable for 1, 2 or 4 way interleave::
> -device cxl-type3,bus=swport3,persistent-memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem3,sn=0x4 \
> -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
>
> +An example of 4 type3 devices with volatile memory below a switch. Two of the devices
> +use HDM-DB for coherence, which requires operating in Flit mode::
> +
> + qemu-system-x86_64 -M q35,cxl=on -m 4G,maxmem=8G,slots=8 -smp 4 \
> + ...
> + -object memory-backend-ram,id=cxl-mem0,share=on,size=256M \
> + -object memory-backend-ram,id=cxl-mem1,share=on,size=256M \
> + -object memory-backend-ram,id=cxl-mem2,share=on,size=256M \
> + -object memory-backend-ram,id=cxl-mem3,share=on,size=256M \
> + -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
> + -device cxl-rp,port=0,bus=cxl.1,id=root_port0,chassis=0,slot=0 \
> + -device cxl-rp,port=1,bus=cxl.1,id=root_port1,chassis=0,slot=1 \
> + -device cxl-upstream,bus=root_port0,id=us0,x-256b-flit=on \
> + -device cxl-downstream,port=0,bus=us0,id=swport0,chassis=0,slot=4 \
> + -device cxl-type3,bus=swport0,volatile-memdev=cxl-mem0,id=cxl-mem0,sn=0x1,x-256b-flit=on,hdm-db=on \
> + -device cxl-downstream,port=1,bus=us0,id=swport1,chassis=0,slot=5 \
> + -device cxl-type3,bus=swport1,volatile-memdev=cxl-mem1,id=cxl-mem1,sn=0x2,x-256b-flit=on,hdm-db=on \
> + -device cxl-downstream,port=2,bus=us0,id=swport2,chassis=0,slot=6 \
> + -device cxl-type3,bus=swport2,volatile-memdev=cxl-mem2,id=cxl-mem2,sn=0x3 \
> + -device cxl-downstream,port=3,bus=us0,id=swport3,chassis=0,slot=7 \
> + -device cxl-type3,bus=swport3,volatile-memdev=cxl-mem3,id=cxl-mem3,sn=0x4 \
> + -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> +
> A simple arm/virt example featuring a single direct connected CXL Type 3
> Volatile Memory device::
>
> diff --git a/include/hw/cxl/cxl_component.h b/include/hw/cxl/cxl_component.h
> index 1f167d3ef79b..ffc82202206c 100644
> --- a/include/hw/cxl/cxl_component.h
> +++ b/include/hw/cxl/cxl_component.h
> @@ -67,6 +67,8 @@ CXLx_CAPABILITY_HEADER(LINK, 2)
> CXLx_CAPABILITY_HEADER(HDM, 3)
> CXLx_CAPABILITY_HEADER(EXTSEC, 4)
> CXLx_CAPABILITY_HEADER(SNOOP, 5)
> +CXLx_CAPABILITY_HEADER(BI_RT, 6)
> +CXLx_CAPABILITY_HEADER(BI_DECODER, 7)
>
> /*
> * Capability structures contain the actual registers that the CXL component
> @@ -211,10 +213,55 @@ HDM_DECODER_INIT(3);
> (CXL_IDE_REGISTERS_OFFSET + CXL_IDE_REGISTERS_SIZE)
> #define CXL_SNOOP_REGISTERS_SIZE 0x8
>
> -QEMU_BUILD_BUG_MSG((CXL_SNOOP_REGISTERS_OFFSET +
> - CXL_SNOOP_REGISTERS_SIZE) >= 0x1000,
> +#define CXL_BI_RT_CAP_VERSION 1
> +#define CXL_BI_RT_REGISTERS_OFFSET \
> + (CXL_SNOOP_REGISTERS_OFFSET + CXL_SNOOP_REGISTERS_SIZE)
> +#define CXL_BI_RT_REGISTERS_SIZE 0xC
> +
> +REG32(CXL_BI_RT_CAPABILITY, CXL_BI_RT_REGISTERS_OFFSET)
> + FIELD(CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 0, 1)
> +REG32(CXL_BI_RT_CTRL, CXL_BI_RT_REGISTERS_OFFSET + 0x4)
> + FIELD(CXL_BI_RT_CTRL, COMMIT, 0, 1)
> +REG32(CXL_BI_RT_STATUS, CXL_BI_RT_REGISTERS_OFFSET + 0x8)
> + FIELD(CXL_BI_RT_STATUS, COMMITTED, 0, 1)
> + FIELD(CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 1, 1)
> + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 8, 4)
> + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 12, 4)
> +
> +/* CXL r3.2 8.2.4.27 - CXL BI Decoder Capability Structure */
> +#define CXL_BI_DECODER_CAP_VERSION 1
> +#define CXL_BI_DECODER_REGISTERS_OFFSET \
> + (CXL_BI_RT_REGISTERS_OFFSET + CXL_BI_RT_REGISTERS_SIZE)
> +#define CXL_BI_DECODER_REGISTERS_SIZE 0xC
> +
> +REG32(CXL_BI_DECODER_CAPABILITY, CXL_BI_DECODER_REGISTERS_OFFSET)
> + FIELD(CXL_BI_DECODER_CAPABILITY, HDM_D, 0, 1)
> + FIELD(CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT, 1, 1)
> +REG32(CXL_BI_DECODER_CTRL, CXL_BI_DECODER_REGISTERS_OFFSET + 0x4)
> + FIELD(CXL_BI_DECODER_CTRL, BI_FW, 0, 1)
> + FIELD(CXL_BI_DECODER_CTRL, BI_ENABLE, 1, 1)
> + FIELD(CXL_BI_DECODER_CTRL, COMMIT, 2, 1)
> +REG32(CXL_BI_DECODER_STATUS, CXL_BI_DECODER_REGISTERS_OFFSET + 0x8)
> + FIELD(CXL_BI_DECODER_STATUS, COMMITTED, 0, 1)
> + FIELD(CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 1, 1)
> + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 8, 4)
> + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 12, 4)
> +
> +QEMU_BUILD_BUG_MSG((CXL_BI_DECODER_REGISTERS_OFFSET +
> + CXL_BI_DECODER_REGISTERS_SIZE) >= 0x1000,
> "No space for registers");
>
> +/* track BI explicit commit handling for route table and decoder */
> +enum {
> + CXL_BISTATE_RT = 0,
> + CXL_BISTATE_DECODER,
> + CXL_BISTATE_MAX
> +};
> +
> +typedef struct bi_state {
> + uint64_t last_commit; /* last 0->1 transition */
> +} BIState;
> +
> typedef struct component_registers {
> /*
> * Main memory region to be registered with QEMU core.
> @@ -259,6 +306,7 @@ typedef struct cxl_component {
> };
>
> CDATObject cdat;
> + BIState bi_state[CXL_BISTATE_MAX];
> } CXLComponentState;
>
> void cxl_component_register_block_init(Object *obj,
> @@ -266,7 +314,7 @@ void cxl_component_register_block_init(Object *obj,
> const char *type);
> void cxl_component_register_init_common(uint32_t *reg_state,
> uint32_t *write_msk,
> - enum reg_type type);
> + enum reg_type type, bool bi);
>
> void cxl_component_create_dvsec(CXLComponentState *cxl_cstate,
> enum reg_type cxl_dev_type, uint16_t length,
> diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
> index 7d9236db8c85..393f3122173b 100644
> --- a/include/hw/cxl/cxl_device.h
> +++ b/include/hw/cxl/cxl_device.h
> @@ -770,6 +770,9 @@ struct CXLType3Dev {
> CXLMemSparingReadAttrs rank_sparing_attrs;
> CXLMemSparingWriteAttrs rank_sparing_wr_attrs;
>
> + /* BI flows */
> + bool hdmdb;
> +
> struct dynamic_capacity {
> HostMemoryBackend *host_dc;
> AddressSpace host_dc_as;
> diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> index 91770f103a85..a7d36e1128c2 100644
> --- a/hw/cxl/cxl-component-utils.c
> +++ b/hw/cxl/cxl-component-utils.c
> @@ -71,10 +71,40 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> case 4:
> if (cregs->special_ops && cregs->special_ops->read) {
> return cregs->special_ops->read(cxl_cstate, offset, 4);
> - } else {
> - QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> - return cregs->cache_mem_registers[offset / 4];
> }
> +
> + QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> +
> + if (offset == A_CXL_BI_RT_STATUS ||
> + offset == A_CXL_BI_DECODER_STATUS) {
> + int type;
> + uint64_t started;
> +
> + type = (offset == A_CXL_BI_RT_STATUS) ?
> + CXL_BISTATE_RT : CXL_BISTATE_DECODER;
> + started = cxl_cstate->bi_state[type].last_commit;
> +
> + if (started) {
> + uint32_t *cache_mem = cregs->cache_mem_registers;
> + uint32_t val = cache_mem[offset / 4];
> + uint64_t now;
> + int set;
> +
> + now = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> + /* arbitrary 100 ms to do the commit */
> + set = !!(now >= started + 100);
> +
> + if (offset == A_CXL_BI_RT_STATUS) {
> + val = FIELD_DP32(val, CXL_BI_RT_STATUS, COMMITTED, set);
> + } else {
> + val = FIELD_DP32(val, CXL_BI_DECODER_STATUS, COMMITTED,
> + set);
> + }
> + stl_le_p((uint8_t *)cache_mem + offset, val);
> + }
> + }
> +
> + return cregs->cache_mem_registers[offset / 4];
> case 8:
> qemu_log_mask(LOG_UNIMP,
> "CXL 8 byte cache mem registers not implemented\n");
> @@ -118,6 +148,47 @@ static void dumb_hdm_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> stl_le_p((uint8_t *)cache_mem + offset, value);
> }
>
> +static void bi_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> + uint32_t value)
> +{
> + ComponentRegisters *cregs = &cxl_cstate->crb;
> + uint32_t sts, *cache_mem = cregs->cache_mem_registers;
> + bool to_commit = false;
> + int type = 0; /* Unused value - work around for compiler warning */
> +
> + switch (offset) {
> + case A_CXL_BI_RT_CTRL:
> + to_commit = FIELD_EX32(value, CXL_BI_RT_CTRL, COMMIT);
> + if (to_commit) {
> + sts = cxl_cache_mem_read_reg(cxl_cstate,
> + R_CXL_BI_RT_STATUS, 4);
> + sts = FIELD_DP32(sts, CXL_BI_RT_STATUS, COMMITTED, 0);
> + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_RT_STATUS, sts);
> + type = CXL_BISTATE_RT;
> + }
> + break;
> + case A_CXL_BI_DECODER_CTRL:
> + to_commit = FIELD_EX32(value, CXL_BI_DECODER_CTRL, COMMIT);
> + if (to_commit) {
> + sts = cxl_cache_mem_read_reg(cxl_cstate,
> + R_CXL_BI_DECODER_STATUS, 4);
> + sts = FIELD_DP32(sts, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_DECODER_STATUS, sts);
> + type = CXL_BISTATE_DECODER;
> + }
> + break;
> + default:
> + break;
> + }
> +
> + if (to_commit) {
> + cxl_cstate->bi_state[type].last_commit =
> + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> + }
> +
> + stl_le_p((uint8_t *)cache_mem + offset, value);
> +}
> +
> static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> unsigned size)
> {
> @@ -141,6 +212,9 @@ static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> if (offset >= A_CXL_HDM_DECODER_CAPABILITY &&
> offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) {
> dumb_hdm_handler(cxl_cstate, offset, value);
> + } else if (offset == A_CXL_BI_RT_CTRL ||
> + offset == A_CXL_BI_DECODER_CTRL) {
> + bi_handler(cxl_cstate, offset, value);
> } else {
> cregs->cache_mem_registers[offset / 4] = value;
> }
> @@ -230,7 +304,7 @@ static void ras_init_common(uint32_t *reg_state, uint32_t *write_msk)
> }
>
> static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> - enum reg_type type)
> + enum reg_type type, bool bi)
> {
> int decoder_count = CXL_HDM_DECODER_COUNT;
> int hdm_inc = R_CXL_HDM_DECODER1_BASE_LO - R_CXL_HDM_DECODER0_BASE_LO;
> @@ -255,7 +329,9 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> UIO_DECODER_COUNT, 0);
> ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, MEMDATA_NXM_CAP, 0);
> ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY,
> - SUPPORTED_COHERENCY_MODEL, 0); /* Unknown */
> + SUPPORTED_COHERENCY_MODEL,
> + /* host+dev or Unknown */
> + type == CXL2_TYPE3_DEVICE && bi ? 3 : 0);
> ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_GLOBAL_CONTROL,
> HDM_DECODER_ENABLE, 0);
> write_msk[R_CXL_HDM_DECODER_GLOBAL_CONTROL] = 0x3;
> @@ -278,9 +354,43 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> }
> }
>
> +static void bi_rt_init_common(uint32_t *reg_state, uint32_t *write_msk)
> +{
> + /* switch usp must commit the new BI-ID, timeout of 2secs */
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 1);
> +
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CTRL, COMMIT, 0);
> + write_msk[R_CXL_BI_RT_CTRL] = 0x1;
> +
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMITTED, 0);
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 0);
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 0x6);
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 0x2);
> +}
> +
> +static void bi_decoder_init_common(uint32_t *reg_state, uint32_t *write_msk,
> + enum reg_type type)
> +{
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, HDM_D, 0);
> + /* switch dsp must commit the new BI-ID, timeout of 2secs */
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT,
> + (type != CXL2_ROOT_PORT && type != CXL2_TYPE3_DEVICE));
> +
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_FW, 0);
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_ENABLE, 0);
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, COMMIT, 0);
> + write_msk[R_CXL_BI_DECODER_CTRL] = 0x7;
> +
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 0);
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 0x6);
> + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 0x2);
> +}
> +
> void cxl_component_register_init_common(uint32_t *reg_state,
> uint32_t *write_msk,
> - enum reg_type type)
> + enum reg_type type,
> + bool bi)
> {
> int caps = 0;
>
> @@ -320,7 +430,7 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> case CXL2_LOGICAL_DEVICE:
> /* + HDM */
> init_cap_reg(HDM, 5, 1);
> - hdm_init_common(reg_state, write_msk, type);
> + hdm_init_common(reg_state, write_msk, type, bi);
> /* fallthrough */
> case CXL2_DOWNSTREAM_PORT:
> case CXL2_DEVICE:
> @@ -335,6 +445,24 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> abort();
> }
>
> + /* back invalidate */
> + if (bi) {
> + switch (type) {
> + case CXL2_UPSTREAM_PORT:
> + init_cap_reg(BI_RT, 11, CXL_BI_RT_CAP_VERSION);
> + bi_rt_init_common(reg_state, write_msk);
> + break;
> + case CXL2_ROOT_PORT:
> + case CXL2_DOWNSTREAM_PORT:
> + case CXL2_TYPE3_DEVICE:
> + init_cap_reg(BI_DECODER, 12, CXL_BI_DECODER_CAP_VERSION);
> + bi_decoder_init_common(reg_state, write_msk, type);
> + break;
> + default:
> + break;
> + }
> + }
> +
> ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, ARRAY_SIZE, caps);
> #undef init_cap_reg
> }
> diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
> index 3c7ecd8c48bc..3f09c589ae58 100644
> --- a/hw/mem/cxl_type3.c
> +++ b/hw/mem/cxl_type3.c
> @@ -748,6 +748,11 @@ static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
> return false;
> }
>
> + if (!ct3d->flitmode && ct3d->hdmdb) {
> + error_setg(errp, "hdm-db requires operating in 256b flit");
> + return false;
> + }
> +
> if (ct3d->hostvmem) {
> MemoryRegion *vmr;
> char *v_name;
> @@ -1317,7 +1322,8 @@ static void ct3d_reset(DeviceState *dev)
>
> pcie_cap_fill_link_ep_usp(PCI_DEVICE(dev), ct3d->width, ct3d->speed,
> ct3d->flitmode);
> - cxl_component_register_init_common(reg_state, write_msk, CXL2_TYPE3_DEVICE);
> + cxl_component_register_init_common(reg_state, write_msk,
> + CXL2_TYPE3_DEVICE, ct3d->hdmdb);
> cxl_device_register_init_t3(ct3d, CXL_T3_MSIX_MBOX);
>
> /*
> @@ -1356,6 +1362,7 @@ static const Property ct3_props[] = {
> DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLType3Dev,
> width, PCIE_LINK_WIDTH_16),
> DEFINE_PROP_BOOL("x-256b-flit", CXLType3Dev, flitmode, false),
> + DEFINE_PROP_BOOL("hdm-db", CXLType3Dev, hdmdb, false),
> };
>
> static uint64_t get_lsa_size(CXLType3Dev *ct3d)
> diff --git a/hw/pci-bridge/cxl_downstream.c b/hw/pci-bridge/cxl_downstream.c
> index 64086d8ec2f2..320818a8f1ce 100644
> --- a/hw/pci-bridge/cxl_downstream.c
> +++ b/hw/pci-bridge/cxl_downstream.c
> @@ -39,7 +39,7 @@ static void latch_registers(CXLDownstreamPort *dsp)
> uint32_t *write_msk = dsp->cxl_cstate.crb.cache_mem_regs_write_mask;
>
> cxl_component_register_init_common(reg_state, write_msk,
> - CXL2_DOWNSTREAM_PORT);
> + CXL2_DOWNSTREAM_PORT, true);
> }
>
> /* TODO: Look at sharing this code across all CXL port types */
> diff --git a/hw/pci-bridge/cxl_root_port.c b/hw/pci-bridge/cxl_root_port.c
> index 5641048084a4..e2093ac39ee6 100644
> --- a/hw/pci-bridge/cxl_root_port.c
> +++ b/hw/pci-bridge/cxl_root_port.c
> @@ -101,7 +101,8 @@ static void latch_registers(CXLRootPort *crp)
> uint32_t *reg_state = crp->cxl_cstate.crb.cache_mem_registers;
> uint32_t *write_msk = crp->cxl_cstate.crb.cache_mem_regs_write_mask;
>
> - cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT);
> + cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT,
> + true);
> }
>
> static void build_dvsecs(PCIDevice *d, CXLComponentState *cxl)
> diff --git a/hw/pci-bridge/cxl_upstream.c b/hw/pci-bridge/cxl_upstream.c
> index c352d11dc7b7..fb8d19539c9f 100644
> --- a/hw/pci-bridge/cxl_upstream.c
> +++ b/hw/pci-bridge/cxl_upstream.c
> @@ -90,7 +90,7 @@ static void latch_registers(CXLUpstreamPort *usp)
> uint32_t *write_msk = usp->cxl_cstate.crb.cache_mem_regs_write_mask;
>
> cxl_component_register_init_common(reg_state, write_msk,
> - CXL2_UPSTREAM_PORT);
> + CXL2_UPSTREAM_PORT, usp->flitmode);
> ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, TARGET_COUNT, 8);
> }
>
> diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
> index b6e2eb796951..11623a5666f6 100644
> --- a/hw/pci-bridge/pci_expander_bridge.c
> +++ b/hw/pci-bridge/pci_expander_bridge.c
> @@ -300,7 +300,7 @@ static void pxb_cxl_dev_reset(DeviceState *dev)
> uint32_t *write_msk = cxl_cstate->crb.cache_mem_regs_write_mask;
> int dsp_count = 0;
>
> - cxl_component_register_init_common(reg_state, write_msk, CXL2_RC);
> + cxl_component_register_init_common(reg_state, write_msk, CXL2_RC, false);
> /*
> * The CXL specification allows for host bridges with no HDM decoders
> * if they only have a single root port.
> --
> 2.51.0
On Wed, Feb 04, 2026 at 08:24:55AM -0500, Michael S. Tsirkin wrote:
> On Wed, Feb 04, 2026 at 12:12:14PM +0000, Jonathan Cameron wrote:
> > From: Davidlohr Bueso <dave@stgolabs.net>
> >
> > Add basic plumbing for memory expander devices that support Back
> > Invalidation. This introduces a 'hdm-db=on|off' parameter and
> > exposes the relevant BI RT/Decoder component cachemem registers.
> >
> > Some noteworthy properties:
> > - Devices require enabling Flit mode across the CXL topology.
> > - Explicit BI-ID commit is required.
> > - HDM decoder support both host and dev coherency models.
> >
> > Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
> > Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>
> more troubles:
> https://gitlab.com/mstredhat/qemu/-/jobs/12984846000
clang just as unhappy:
https://gitlab.com/mstredhat/qemu/-/jobs/12984846060
>
> > ---
> > v6: Initialize type variable to avoid a false compiler warning
> > from some versions of gcc. (Michael Tsirkin)
> > ---
> > docs/system/devices/cxl.rst | 23 +++++
> > include/hw/cxl/cxl_component.h | 54 ++++++++++-
> > include/hw/cxl/cxl_device.h | 3 +
> > hw/cxl/cxl-component-utils.c | 142 ++++++++++++++++++++++++++--
> > hw/mem/cxl_type3.c | 9 +-
> > hw/pci-bridge/cxl_downstream.c | 2 +-
> > hw/pci-bridge/cxl_root_port.c | 3 +-
> > hw/pci-bridge/cxl_upstream.c | 2 +-
> > hw/pci-bridge/pci_expander_bridge.c | 2 +-
> > 9 files changed, 225 insertions(+), 15 deletions(-)
> >
> > diff --git a/docs/system/devices/cxl.rst b/docs/system/devices/cxl.rst
> > index ca15a0da1c1d..9d0771cdfd73 100644
> > --- a/docs/system/devices/cxl.rst
> > +++ b/docs/system/devices/cxl.rst
> > @@ -384,6 +384,29 @@ An example of 4 devices below a switch suitable for 1, 2 or 4 way interleave::
> > -device cxl-type3,bus=swport3,persistent-memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem3,sn=0x4 \
> > -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> >
> > +An example of 4 type3 devices with volatile memory below a switch. Two of the devices
> > +use HDM-DB for coherence, which requires operating in Flit mode::
> > +
> > + qemu-system-x86_64 -M q35,cxl=on -m 4G,maxmem=8G,slots=8 -smp 4 \
> > + ...
> > + -object memory-backend-ram,id=cxl-mem0,share=on,size=256M \
> > + -object memory-backend-ram,id=cxl-mem1,share=on,size=256M \
> > + -object memory-backend-ram,id=cxl-mem2,share=on,size=256M \
> > + -object memory-backend-ram,id=cxl-mem3,share=on,size=256M \
> > + -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
> > + -device cxl-rp,port=0,bus=cxl.1,id=root_port0,chassis=0,slot=0 \
> > + -device cxl-rp,port=1,bus=cxl.1,id=root_port1,chassis=0,slot=1 \
> > + -device cxl-upstream,bus=root_port0,id=us0,x-256b-flit=on \
> > + -device cxl-downstream,port=0,bus=us0,id=swport0,chassis=0,slot=4 \
> > + -device cxl-type3,bus=swport0,volatile-memdev=cxl-mem0,id=cxl-mem0,sn=0x1,x-256b-flit=on,hdm-db=on \
> > + -device cxl-downstream,port=1,bus=us0,id=swport1,chassis=0,slot=5 \
> > + -device cxl-type3,bus=swport1,volatile-memdev=cxl-mem1,id=cxl-mem1,sn=0x2,x-256b-flit=on,hdm-db=on \
> > + -device cxl-downstream,port=2,bus=us0,id=swport2,chassis=0,slot=6 \
> > + -device cxl-type3,bus=swport2,volatile-memdev=cxl-mem2,id=cxl-mem2,sn=0x3 \
> > + -device cxl-downstream,port=3,bus=us0,id=swport3,chassis=0,slot=7 \
> > + -device cxl-type3,bus=swport3,volatile-memdev=cxl-mem3,id=cxl-mem3,sn=0x4 \
> > + -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > +
> > A simple arm/virt example featuring a single direct connected CXL Type 3
> > Volatile Memory device::
> >
> > diff --git a/include/hw/cxl/cxl_component.h b/include/hw/cxl/cxl_component.h
> > index 1f167d3ef79b..ffc82202206c 100644
> > --- a/include/hw/cxl/cxl_component.h
> > +++ b/include/hw/cxl/cxl_component.h
> > @@ -67,6 +67,8 @@ CXLx_CAPABILITY_HEADER(LINK, 2)
> > CXLx_CAPABILITY_HEADER(HDM, 3)
> > CXLx_CAPABILITY_HEADER(EXTSEC, 4)
> > CXLx_CAPABILITY_HEADER(SNOOP, 5)
> > +CXLx_CAPABILITY_HEADER(BI_RT, 6)
> > +CXLx_CAPABILITY_HEADER(BI_DECODER, 7)
> >
> > /*
> > * Capability structures contain the actual registers that the CXL component
> > @@ -211,10 +213,55 @@ HDM_DECODER_INIT(3);
> > (CXL_IDE_REGISTERS_OFFSET + CXL_IDE_REGISTERS_SIZE)
> > #define CXL_SNOOP_REGISTERS_SIZE 0x8
> >
> > -QEMU_BUILD_BUG_MSG((CXL_SNOOP_REGISTERS_OFFSET +
> > - CXL_SNOOP_REGISTERS_SIZE) >= 0x1000,
> > +#define CXL_BI_RT_CAP_VERSION 1
> > +#define CXL_BI_RT_REGISTERS_OFFSET \
> > + (CXL_SNOOP_REGISTERS_OFFSET + CXL_SNOOP_REGISTERS_SIZE)
> > +#define CXL_BI_RT_REGISTERS_SIZE 0xC
> > +
> > +REG32(CXL_BI_RT_CAPABILITY, CXL_BI_RT_REGISTERS_OFFSET)
> > + FIELD(CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 0, 1)
> > +REG32(CXL_BI_RT_CTRL, CXL_BI_RT_REGISTERS_OFFSET + 0x4)
> > + FIELD(CXL_BI_RT_CTRL, COMMIT, 0, 1)
> > +REG32(CXL_BI_RT_STATUS, CXL_BI_RT_REGISTERS_OFFSET + 0x8)
> > + FIELD(CXL_BI_RT_STATUS, COMMITTED, 0, 1)
> > + FIELD(CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 12, 4)
> > +
> > +/* CXL r3.2 8.2.4.27 - CXL BI Decoder Capability Structure */
> > +#define CXL_BI_DECODER_CAP_VERSION 1
> > +#define CXL_BI_DECODER_REGISTERS_OFFSET \
> > + (CXL_BI_RT_REGISTERS_OFFSET + CXL_BI_RT_REGISTERS_SIZE)
> > +#define CXL_BI_DECODER_REGISTERS_SIZE 0xC
> > +
> > +REG32(CXL_BI_DECODER_CAPABILITY, CXL_BI_DECODER_REGISTERS_OFFSET)
> > + FIELD(CXL_BI_DECODER_CAPABILITY, HDM_D, 0, 1)
> > + FIELD(CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT, 1, 1)
> > +REG32(CXL_BI_DECODER_CTRL, CXL_BI_DECODER_REGISTERS_OFFSET + 0x4)
> > + FIELD(CXL_BI_DECODER_CTRL, BI_FW, 0, 1)
> > + FIELD(CXL_BI_DECODER_CTRL, BI_ENABLE, 1, 1)
> > + FIELD(CXL_BI_DECODER_CTRL, COMMIT, 2, 1)
> > +REG32(CXL_BI_DECODER_STATUS, CXL_BI_DECODER_REGISTERS_OFFSET + 0x8)
> > + FIELD(CXL_BI_DECODER_STATUS, COMMITTED, 0, 1)
> > + FIELD(CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 12, 4)
> > +
> > +QEMU_BUILD_BUG_MSG((CXL_BI_DECODER_REGISTERS_OFFSET +
> > + CXL_BI_DECODER_REGISTERS_SIZE) >= 0x1000,
> > "No space for registers");
> >
> > +/* track BI explicit commit handling for route table and decoder */
> > +enum {
> > + CXL_BISTATE_RT = 0,
> > + CXL_BISTATE_DECODER,
> > + CXL_BISTATE_MAX
> > +};
> > +
> > +typedef struct bi_state {
> > + uint64_t last_commit; /* last 0->1 transition */
> > +} BIState;
> > +
> > typedef struct component_registers {
> > /*
> > * Main memory region to be registered with QEMU core.
> > @@ -259,6 +306,7 @@ typedef struct cxl_component {
> > };
> >
> > CDATObject cdat;
> > + BIState bi_state[CXL_BISTATE_MAX];
> > } CXLComponentState;
> >
> > void cxl_component_register_block_init(Object *obj,
> > @@ -266,7 +314,7 @@ void cxl_component_register_block_init(Object *obj,
> > const char *type);
> > void cxl_component_register_init_common(uint32_t *reg_state,
> > uint32_t *write_msk,
> > - enum reg_type type);
> > + enum reg_type type, bool bi);
> >
> > void cxl_component_create_dvsec(CXLComponentState *cxl_cstate,
> > enum reg_type cxl_dev_type, uint16_t length,
> > diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
> > index 7d9236db8c85..393f3122173b 100644
> > --- a/include/hw/cxl/cxl_device.h
> > +++ b/include/hw/cxl/cxl_device.h
> > @@ -770,6 +770,9 @@ struct CXLType3Dev {
> > CXLMemSparingReadAttrs rank_sparing_attrs;
> > CXLMemSparingWriteAttrs rank_sparing_wr_attrs;
> >
> > + /* BI flows */
> > + bool hdmdb;
> > +
> > struct dynamic_capacity {
> > HostMemoryBackend *host_dc;
> > AddressSpace host_dc_as;
> > diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> > index 91770f103a85..a7d36e1128c2 100644
> > --- a/hw/cxl/cxl-component-utils.c
> > +++ b/hw/cxl/cxl-component-utils.c
> > @@ -71,10 +71,40 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> > case 4:
> > if (cregs->special_ops && cregs->special_ops->read) {
> > return cregs->special_ops->read(cxl_cstate, offset, 4);
> > - } else {
> > - QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > - return cregs->cache_mem_registers[offset / 4];
> > }
> > +
> > + QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > +
> > + if (offset == A_CXL_BI_RT_STATUS ||
> > + offset == A_CXL_BI_DECODER_STATUS) {
> > + int type;
> > + uint64_t started;
> > +
> > + type = (offset == A_CXL_BI_RT_STATUS) ?
> > + CXL_BISTATE_RT : CXL_BISTATE_DECODER;
> > + started = cxl_cstate->bi_state[type].last_commit;
> > +
> > + if (started) {
> > + uint32_t *cache_mem = cregs->cache_mem_registers;
> > + uint32_t val = cache_mem[offset / 4];
> > + uint64_t now;
> > + int set;
> > +
> > + now = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > + /* arbitrary 100 ms to do the commit */
> > + set = !!(now >= started + 100);
> > +
> > + if (offset == A_CXL_BI_RT_STATUS) {
> > + val = FIELD_DP32(val, CXL_BI_RT_STATUS, COMMITTED, set);
> > + } else {
> > + val = FIELD_DP32(val, CXL_BI_DECODER_STATUS, COMMITTED,
> > + set);
> > + }
> > + stl_le_p((uint8_t *)cache_mem + offset, val);
> > + }
> > + }
> > +
> > + return cregs->cache_mem_registers[offset / 4];
> > case 8:
> > qemu_log_mask(LOG_UNIMP,
> > "CXL 8 byte cache mem registers not implemented\n");
> > @@ -118,6 +148,47 @@ static void dumb_hdm_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > stl_le_p((uint8_t *)cache_mem + offset, value);
> > }
> >
> > +static void bi_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > + uint32_t value)
> > +{
> > + ComponentRegisters *cregs = &cxl_cstate->crb;
> > + uint32_t sts, *cache_mem = cregs->cache_mem_registers;
> > + bool to_commit = false;
> > + int type = 0; /* Unused value - work around for compiler warning */
> > +
> > + switch (offset) {
> > + case A_CXL_BI_RT_CTRL:
> > + to_commit = FIELD_EX32(value, CXL_BI_RT_CTRL, COMMIT);
> > + if (to_commit) {
> > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > + R_CXL_BI_RT_STATUS, 4);
> > + sts = FIELD_DP32(sts, CXL_BI_RT_STATUS, COMMITTED, 0);
> > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_RT_STATUS, sts);
> > + type = CXL_BISTATE_RT;
> > + }
> > + break;
> > + case A_CXL_BI_DECODER_CTRL:
> > + to_commit = FIELD_EX32(value, CXL_BI_DECODER_CTRL, COMMIT);
> > + if (to_commit) {
> > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > + R_CXL_BI_DECODER_STATUS, 4);
> > + sts = FIELD_DP32(sts, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_DECODER_STATUS, sts);
> > + type = CXL_BISTATE_DECODER;
> > + }
> > + break;
> > + default:
> > + break;
> > + }
> > +
> > + if (to_commit) {
> > + cxl_cstate->bi_state[type].last_commit =
> > + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > + }
> > +
> > + stl_le_p((uint8_t *)cache_mem + offset, value);
> > +}
> > +
> > static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > unsigned size)
> > {
> > @@ -141,6 +212,9 @@ static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > if (offset >= A_CXL_HDM_DECODER_CAPABILITY &&
> > offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) {
> > dumb_hdm_handler(cxl_cstate, offset, value);
> > + } else if (offset == A_CXL_BI_RT_CTRL ||
> > + offset == A_CXL_BI_DECODER_CTRL) {
> > + bi_handler(cxl_cstate, offset, value);
> > } else {
> > cregs->cache_mem_registers[offset / 4] = value;
> > }
> > @@ -230,7 +304,7 @@ static void ras_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > }
> >
> > static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > - enum reg_type type)
> > + enum reg_type type, bool bi)
> > {
> > int decoder_count = CXL_HDM_DECODER_COUNT;
> > int hdm_inc = R_CXL_HDM_DECODER1_BASE_LO - R_CXL_HDM_DECODER0_BASE_LO;
> > @@ -255,7 +329,9 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > UIO_DECODER_COUNT, 0);
> > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, MEMDATA_NXM_CAP, 0);
> > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY,
> > - SUPPORTED_COHERENCY_MODEL, 0); /* Unknown */
> > + SUPPORTED_COHERENCY_MODEL,
> > + /* host+dev or Unknown */
> > + type == CXL2_TYPE3_DEVICE && bi ? 3 : 0);
> > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_GLOBAL_CONTROL,
> > HDM_DECODER_ENABLE, 0);
> > write_msk[R_CXL_HDM_DECODER_GLOBAL_CONTROL] = 0x3;
> > @@ -278,9 +354,43 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > }
> > }
> >
> > +static void bi_rt_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > +{
> > + /* switch usp must commit the new BI-ID, timeout of 2secs */
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 1);
> > +
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CTRL, COMMIT, 0);
> > + write_msk[R_CXL_BI_RT_CTRL] = 0x1;
> > +
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMITTED, 0);
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 0);
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 0x6);
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 0x2);
> > +}
> > +
> > +static void bi_decoder_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > + enum reg_type type)
> > +{
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, HDM_D, 0);
> > + /* switch dsp must commit the new BI-ID, timeout of 2secs */
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT,
> > + (type != CXL2_ROOT_PORT && type != CXL2_TYPE3_DEVICE));
> > +
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_FW, 0);
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_ENABLE, 0);
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, COMMIT, 0);
> > + write_msk[R_CXL_BI_DECODER_CTRL] = 0x7;
> > +
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 0);
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 0x6);
> > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 0x2);
> > +}
> > +
> > void cxl_component_register_init_common(uint32_t *reg_state,
> > uint32_t *write_msk,
> > - enum reg_type type)
> > + enum reg_type type,
> > + bool bi)
> > {
> > int caps = 0;
> >
> > @@ -320,7 +430,7 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > case CXL2_LOGICAL_DEVICE:
> > /* + HDM */
> > init_cap_reg(HDM, 5, 1);
> > - hdm_init_common(reg_state, write_msk, type);
> > + hdm_init_common(reg_state, write_msk, type, bi);
> > /* fallthrough */
> > case CXL2_DOWNSTREAM_PORT:
> > case CXL2_DEVICE:
> > @@ -335,6 +445,24 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > abort();
> > }
> >
> > + /* back invalidate */
> > + if (bi) {
> > + switch (type) {
> > + case CXL2_UPSTREAM_PORT:
> > + init_cap_reg(BI_RT, 11, CXL_BI_RT_CAP_VERSION);
> > + bi_rt_init_common(reg_state, write_msk);
> > + break;
> > + case CXL2_ROOT_PORT:
> > + case CXL2_DOWNSTREAM_PORT:
> > + case CXL2_TYPE3_DEVICE:
> > + init_cap_reg(BI_DECODER, 12, CXL_BI_DECODER_CAP_VERSION);
> > + bi_decoder_init_common(reg_state, write_msk, type);
> > + break;
> > + default:
> > + break;
> > + }
> > + }
> > +
> > ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, ARRAY_SIZE, caps);
> > #undef init_cap_reg
> > }
> > diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
> > index 3c7ecd8c48bc..3f09c589ae58 100644
> > --- a/hw/mem/cxl_type3.c
> > +++ b/hw/mem/cxl_type3.c
> > @@ -748,6 +748,11 @@ static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
> > return false;
> > }
> >
> > + if (!ct3d->flitmode && ct3d->hdmdb) {
> > + error_setg(errp, "hdm-db requires operating in 256b flit");
> > + return false;
> > + }
> > +
> > if (ct3d->hostvmem) {
> > MemoryRegion *vmr;
> > char *v_name;
> > @@ -1317,7 +1322,8 @@ static void ct3d_reset(DeviceState *dev)
> >
> > pcie_cap_fill_link_ep_usp(PCI_DEVICE(dev), ct3d->width, ct3d->speed,
> > ct3d->flitmode);
> > - cxl_component_register_init_common(reg_state, write_msk, CXL2_TYPE3_DEVICE);
> > + cxl_component_register_init_common(reg_state, write_msk,
> > + CXL2_TYPE3_DEVICE, ct3d->hdmdb);
> > cxl_device_register_init_t3(ct3d, CXL_T3_MSIX_MBOX);
> >
> > /*
> > @@ -1356,6 +1362,7 @@ static const Property ct3_props[] = {
> > DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLType3Dev,
> > width, PCIE_LINK_WIDTH_16),
> > DEFINE_PROP_BOOL("x-256b-flit", CXLType3Dev, flitmode, false),
> > + DEFINE_PROP_BOOL("hdm-db", CXLType3Dev, hdmdb, false),
> > };
> >
> > static uint64_t get_lsa_size(CXLType3Dev *ct3d)
> > diff --git a/hw/pci-bridge/cxl_downstream.c b/hw/pci-bridge/cxl_downstream.c
> > index 64086d8ec2f2..320818a8f1ce 100644
> > --- a/hw/pci-bridge/cxl_downstream.c
> > +++ b/hw/pci-bridge/cxl_downstream.c
> > @@ -39,7 +39,7 @@ static void latch_registers(CXLDownstreamPort *dsp)
> > uint32_t *write_msk = dsp->cxl_cstate.crb.cache_mem_regs_write_mask;
> >
> > cxl_component_register_init_common(reg_state, write_msk,
> > - CXL2_DOWNSTREAM_PORT);
> > + CXL2_DOWNSTREAM_PORT, true);
> > }
> >
> > /* TODO: Look at sharing this code across all CXL port types */
> > diff --git a/hw/pci-bridge/cxl_root_port.c b/hw/pci-bridge/cxl_root_port.c
> > index 5641048084a4..e2093ac39ee6 100644
> > --- a/hw/pci-bridge/cxl_root_port.c
> > +++ b/hw/pci-bridge/cxl_root_port.c
> > @@ -101,7 +101,8 @@ static void latch_registers(CXLRootPort *crp)
> > uint32_t *reg_state = crp->cxl_cstate.crb.cache_mem_registers;
> > uint32_t *write_msk = crp->cxl_cstate.crb.cache_mem_regs_write_mask;
> >
> > - cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT);
> > + cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT,
> > + true);
> > }
> >
> > static void build_dvsecs(PCIDevice *d, CXLComponentState *cxl)
> > diff --git a/hw/pci-bridge/cxl_upstream.c b/hw/pci-bridge/cxl_upstream.c
> > index c352d11dc7b7..fb8d19539c9f 100644
> > --- a/hw/pci-bridge/cxl_upstream.c
> > +++ b/hw/pci-bridge/cxl_upstream.c
> > @@ -90,7 +90,7 @@ static void latch_registers(CXLUpstreamPort *usp)
> > uint32_t *write_msk = usp->cxl_cstate.crb.cache_mem_regs_write_mask;
> >
> > cxl_component_register_init_common(reg_state, write_msk,
> > - CXL2_UPSTREAM_PORT);
> > + CXL2_UPSTREAM_PORT, usp->flitmode);
> > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, TARGET_COUNT, 8);
> > }
> >
> > diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
> > index b6e2eb796951..11623a5666f6 100644
> > --- a/hw/pci-bridge/pci_expander_bridge.c
> > +++ b/hw/pci-bridge/pci_expander_bridge.c
> > @@ -300,7 +300,7 @@ static void pxb_cxl_dev_reset(DeviceState *dev)
> > uint32_t *write_msk = cxl_cstate->crb.cache_mem_regs_write_mask;
> > int dsp_count = 0;
> >
> > - cxl_component_register_init_common(reg_state, write_msk, CXL2_RC);
> > + cxl_component_register_init_common(reg_state, write_msk, CXL2_RC, false);
> > /*
> > * The CXL specification allows for host bridges with no HDM decoders
> > * if they only have a single root port.
> > --
> > 2.51.0
On Wed, 4 Feb 2026 08:44:42 -0500
"Michael S. Tsirkin" <mst@redhat.com> wrote:
> On Wed, Feb 04, 2026 at 08:24:55AM -0500, Michael S. Tsirkin wrote:
> > On Wed, Feb 04, 2026 at 12:12:14PM +0000, Jonathan Cameron wrote:
> > > From: Davidlohr Bueso <dave@stgolabs.net>
> > >
> > > Add basic plumbing for memory expander devices that support Back
> > > Invalidation. This introduces a 'hdm-db=on|off' parameter and
> > > exposes the relevant BI RT/Decoder component cachemem registers.
> > >
> > > Some noteworthy properties:
> > > - Devices require enabling Flit mode across the CXL topology.
> > > - Explicit BI-ID commit is required.
> > > - HDM decoder support both host and dev coherency models.
> > >
> > > Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
> > > Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> > > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> >
> > more troubles:
> > https://gitlab.com/mstredhat/qemu/-/jobs/12984846000
>
>
> clang just as unhappy:
>
> https://gitlab.com/mstredhat/qemu/-/jobs/12984846060
They both seem to be clang.
Replicated.
Ah. This old gotcha - at one point I got one of my compiler colleagues to report
it as a clang bug but he lost the argument vs the spec. Though I believe
it is being fixed in the C spec longer term. I can't find the thread
now but we did discuss adding local scope in the macro a while back.
Anyhow work around is to add scope to avoid label for the case statement
being followed by _Static_assert()
Despite smelling like a function, it's not and has special rules...
Would you like a v7 or squash the following in?
Thanks
Jonathan
diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
index a3077184e230..07aabe331c44 100644
--- a/hw/cxl/cxl-component-utils.c
+++ b/hw/cxl/cxl-component-utils.c
@@ -68,7 +68,7 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
ComponentRegisters *cregs = &cxl_cstate->crb;
switch (size) {
- case 4:
+ case 4: {
QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
if (offset == A_CXL_BI_RT_STATUS ||
@@ -101,6 +101,7 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
}
return cregs->cache_mem_registers[offset / 4];
+ }
case 8:
qemu_log_mask(LOG_UNIMP,
"CXL 8 byte cache mem registers not implemented\n");
>
> >
> > > ---
> > > v6: Initialize type variable to avoid a false compiler warning
> > > from some versions of gcc. (Michael Tsirkin)
> > > ---
> > > docs/system/devices/cxl.rst | 23 +++++
> > > include/hw/cxl/cxl_component.h | 54 ++++++++++-
> > > include/hw/cxl/cxl_device.h | 3 +
> > > hw/cxl/cxl-component-utils.c | 142 ++++++++++++++++++++++++++--
> > > hw/mem/cxl_type3.c | 9 +-
> > > hw/pci-bridge/cxl_downstream.c | 2 +-
> > > hw/pci-bridge/cxl_root_port.c | 3 +-
> > > hw/pci-bridge/cxl_upstream.c | 2 +-
> > > hw/pci-bridge/pci_expander_bridge.c | 2 +-
> > > 9 files changed, 225 insertions(+), 15 deletions(-)
> > >
> > > diff --git a/docs/system/devices/cxl.rst b/docs/system/devices/cxl.rst
> > > index ca15a0da1c1d..9d0771cdfd73 100644
> > > --- a/docs/system/devices/cxl.rst
> > > +++ b/docs/system/devices/cxl.rst
> > > @@ -384,6 +384,29 @@ An example of 4 devices below a switch suitable for 1, 2 or 4 way interleave::
> > > -device cxl-type3,bus=swport3,persistent-memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem3,sn=0x4 \
> > > -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > >
> > > +An example of 4 type3 devices with volatile memory below a switch. Two of the devices
> > > +use HDM-DB for coherence, which requires operating in Flit mode::
> > > +
> > > + qemu-system-x86_64 -M q35,cxl=on -m 4G,maxmem=8G,slots=8 -smp 4 \
> > > + ...
> > > + -object memory-backend-ram,id=cxl-mem0,share=on,size=256M \
> > > + -object memory-backend-ram,id=cxl-mem1,share=on,size=256M \
> > > + -object memory-backend-ram,id=cxl-mem2,share=on,size=256M \
> > > + -object memory-backend-ram,id=cxl-mem3,share=on,size=256M \
> > > + -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
> > > + -device cxl-rp,port=0,bus=cxl.1,id=root_port0,chassis=0,slot=0 \
> > > + -device cxl-rp,port=1,bus=cxl.1,id=root_port1,chassis=0,slot=1 \
> > > + -device cxl-upstream,bus=root_port0,id=us0,x-256b-flit=on \
> > > + -device cxl-downstream,port=0,bus=us0,id=swport0,chassis=0,slot=4 \
> > > + -device cxl-type3,bus=swport0,volatile-memdev=cxl-mem0,id=cxl-mem0,sn=0x1,x-256b-flit=on,hdm-db=on \
> > > + -device cxl-downstream,port=1,bus=us0,id=swport1,chassis=0,slot=5 \
> > > + -device cxl-type3,bus=swport1,volatile-memdev=cxl-mem1,id=cxl-mem1,sn=0x2,x-256b-flit=on,hdm-db=on \
> > > + -device cxl-downstream,port=2,bus=us0,id=swport2,chassis=0,slot=6 \
> > > + -device cxl-type3,bus=swport2,volatile-memdev=cxl-mem2,id=cxl-mem2,sn=0x3 \
> > > + -device cxl-downstream,port=3,bus=us0,id=swport3,chassis=0,slot=7 \
> > > + -device cxl-type3,bus=swport3,volatile-memdev=cxl-mem3,id=cxl-mem3,sn=0x4 \
> > > + -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > > +
> > > A simple arm/virt example featuring a single direct connected CXL Type 3
> > > Volatile Memory device::
> > >
> > > diff --git a/include/hw/cxl/cxl_component.h b/include/hw/cxl/cxl_component.h
> > > index 1f167d3ef79b..ffc82202206c 100644
> > > --- a/include/hw/cxl/cxl_component.h
> > > +++ b/include/hw/cxl/cxl_component.h
> > > @@ -67,6 +67,8 @@ CXLx_CAPABILITY_HEADER(LINK, 2)
> > > CXLx_CAPABILITY_HEADER(HDM, 3)
> > > CXLx_CAPABILITY_HEADER(EXTSEC, 4)
> > > CXLx_CAPABILITY_HEADER(SNOOP, 5)
> > > +CXLx_CAPABILITY_HEADER(BI_RT, 6)
> > > +CXLx_CAPABILITY_HEADER(BI_DECODER, 7)
> > >
> > > /*
> > > * Capability structures contain the actual registers that the CXL component
> > > @@ -211,10 +213,55 @@ HDM_DECODER_INIT(3);
> > > (CXL_IDE_REGISTERS_OFFSET + CXL_IDE_REGISTERS_SIZE)
> > > #define CXL_SNOOP_REGISTERS_SIZE 0x8
> > >
> > > -QEMU_BUILD_BUG_MSG((CXL_SNOOP_REGISTERS_OFFSET +
> > > - CXL_SNOOP_REGISTERS_SIZE) >= 0x1000,
> > > +#define CXL_BI_RT_CAP_VERSION 1
> > > +#define CXL_BI_RT_REGISTERS_OFFSET \
> > > + (CXL_SNOOP_REGISTERS_OFFSET + CXL_SNOOP_REGISTERS_SIZE)
> > > +#define CXL_BI_RT_REGISTERS_SIZE 0xC
> > > +
> > > +REG32(CXL_BI_RT_CAPABILITY, CXL_BI_RT_REGISTERS_OFFSET)
> > > + FIELD(CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 0, 1)
> > > +REG32(CXL_BI_RT_CTRL, CXL_BI_RT_REGISTERS_OFFSET + 0x4)
> > > + FIELD(CXL_BI_RT_CTRL, COMMIT, 0, 1)
> > > +REG32(CXL_BI_RT_STATUS, CXL_BI_RT_REGISTERS_OFFSET + 0x8)
> > > + FIELD(CXL_BI_RT_STATUS, COMMITTED, 0, 1)
> > > + FIELD(CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 12, 4)
> > > +
> > > +/* CXL r3.2 8.2.4.27 - CXL BI Decoder Capability Structure */
> > > +#define CXL_BI_DECODER_CAP_VERSION 1
> > > +#define CXL_BI_DECODER_REGISTERS_OFFSET \
> > > + (CXL_BI_RT_REGISTERS_OFFSET + CXL_BI_RT_REGISTERS_SIZE)
> > > +#define CXL_BI_DECODER_REGISTERS_SIZE 0xC
> > > +
> > > +REG32(CXL_BI_DECODER_CAPABILITY, CXL_BI_DECODER_REGISTERS_OFFSET)
> > > + FIELD(CXL_BI_DECODER_CAPABILITY, HDM_D, 0, 1)
> > > + FIELD(CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT, 1, 1)
> > > +REG32(CXL_BI_DECODER_CTRL, CXL_BI_DECODER_REGISTERS_OFFSET + 0x4)
> > > + FIELD(CXL_BI_DECODER_CTRL, BI_FW, 0, 1)
> > > + FIELD(CXL_BI_DECODER_CTRL, BI_ENABLE, 1, 1)
> > > + FIELD(CXL_BI_DECODER_CTRL, COMMIT, 2, 1)
> > > +REG32(CXL_BI_DECODER_STATUS, CXL_BI_DECODER_REGISTERS_OFFSET + 0x8)
> > > + FIELD(CXL_BI_DECODER_STATUS, COMMITTED, 0, 1)
> > > + FIELD(CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 12, 4)
> > > +
> > > +QEMU_BUILD_BUG_MSG((CXL_BI_DECODER_REGISTERS_OFFSET +
> > > + CXL_BI_DECODER_REGISTERS_SIZE) >= 0x1000,
> > > "No space for registers");
> > >
> > > +/* track BI explicit commit handling for route table and decoder */
> > > +enum {
> > > + CXL_BISTATE_RT = 0,
> > > + CXL_BISTATE_DECODER,
> > > + CXL_BISTATE_MAX
> > > +};
> > > +
> > > +typedef struct bi_state {
> > > + uint64_t last_commit; /* last 0->1 transition */
> > > +} BIState;
> > > +
> > > typedef struct component_registers {
> > > /*
> > > * Main memory region to be registered with QEMU core.
> > > @@ -259,6 +306,7 @@ typedef struct cxl_component {
> > > };
> > >
> > > CDATObject cdat;
> > > + BIState bi_state[CXL_BISTATE_MAX];
> > > } CXLComponentState;
> > >
> > > void cxl_component_register_block_init(Object *obj,
> > > @@ -266,7 +314,7 @@ void cxl_component_register_block_init(Object *obj,
> > > const char *type);
> > > void cxl_component_register_init_common(uint32_t *reg_state,
> > > uint32_t *write_msk,
> > > - enum reg_type type);
> > > + enum reg_type type, bool bi);
> > >
> > > void cxl_component_create_dvsec(CXLComponentState *cxl_cstate,
> > > enum reg_type cxl_dev_type, uint16_t length,
> > > diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
> > > index 7d9236db8c85..393f3122173b 100644
> > > --- a/include/hw/cxl/cxl_device.h
> > > +++ b/include/hw/cxl/cxl_device.h
> > > @@ -770,6 +770,9 @@ struct CXLType3Dev {
> > > CXLMemSparingReadAttrs rank_sparing_attrs;
> > > CXLMemSparingWriteAttrs rank_sparing_wr_attrs;
> > >
> > > + /* BI flows */
> > > + bool hdmdb;
> > > +
> > > struct dynamic_capacity {
> > > HostMemoryBackend *host_dc;
> > > AddressSpace host_dc_as;
> > > diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> > > index 91770f103a85..a7d36e1128c2 100644
> > > --- a/hw/cxl/cxl-component-utils.c
> > > +++ b/hw/cxl/cxl-component-utils.c
> > > @@ -71,10 +71,40 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> > > case 4:
> > > if (cregs->special_ops && cregs->special_ops->read) {
> > > return cregs->special_ops->read(cxl_cstate, offset, 4);
> > > - } else {
> > > - QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > > - return cregs->cache_mem_registers[offset / 4];
> > > }
> > > +
> > > + QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > > +
> > > + if (offset == A_CXL_BI_RT_STATUS ||
> > > + offset == A_CXL_BI_DECODER_STATUS) {
> > > + int type;
> > > + uint64_t started;
> > > +
> > > + type = (offset == A_CXL_BI_RT_STATUS) ?
> > > + CXL_BISTATE_RT : CXL_BISTATE_DECODER;
> > > + started = cxl_cstate->bi_state[type].last_commit;
> > > +
> > > + if (started) {
> > > + uint32_t *cache_mem = cregs->cache_mem_registers;
> > > + uint32_t val = cache_mem[offset / 4];
> > > + uint64_t now;
> > > + int set;
> > > +
> > > + now = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > > + /* arbitrary 100 ms to do the commit */
> > > + set = !!(now >= started + 100);
> > > +
> > > + if (offset == A_CXL_BI_RT_STATUS) {
> > > + val = FIELD_DP32(val, CXL_BI_RT_STATUS, COMMITTED, set);
> > > + } else {
> > > + val = FIELD_DP32(val, CXL_BI_DECODER_STATUS, COMMITTED,
> > > + set);
> > > + }
> > > + stl_le_p((uint8_t *)cache_mem + offset, val);
> > > + }
> > > + }
> > > +
> > > + return cregs->cache_mem_registers[offset / 4];
> > > case 8:
> > > qemu_log_mask(LOG_UNIMP,
> > > "CXL 8 byte cache mem registers not implemented\n");
> > > @@ -118,6 +148,47 @@ static void dumb_hdm_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > > stl_le_p((uint8_t *)cache_mem + offset, value);
> > > }
> > >
> > > +static void bi_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > > + uint32_t value)
> > > +{
> > > + ComponentRegisters *cregs = &cxl_cstate->crb;
> > > + uint32_t sts, *cache_mem = cregs->cache_mem_registers;
> > > + bool to_commit = false;
> > > + int type = 0; /* Unused value - work around for compiler warning */
> > > +
> > > + switch (offset) {
> > > + case A_CXL_BI_RT_CTRL:
> > > + to_commit = FIELD_EX32(value, CXL_BI_RT_CTRL, COMMIT);
> > > + if (to_commit) {
> > > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > > + R_CXL_BI_RT_STATUS, 4);
> > > + sts = FIELD_DP32(sts, CXL_BI_RT_STATUS, COMMITTED, 0);
> > > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_RT_STATUS, sts);
> > > + type = CXL_BISTATE_RT;
> > > + }
> > > + break;
> > > + case A_CXL_BI_DECODER_CTRL:
> > > + to_commit = FIELD_EX32(value, CXL_BI_DECODER_CTRL, COMMIT);
> > > + if (to_commit) {
> > > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > > + R_CXL_BI_DECODER_STATUS, 4);
> > > + sts = FIELD_DP32(sts, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_DECODER_STATUS, sts);
> > > + type = CXL_BISTATE_DECODER;
> > > + }
> > > + break;
> > > + default:
> > > + break;
> > > + }
> > > +
> > > + if (to_commit) {
> > > + cxl_cstate->bi_state[type].last_commit =
> > > + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > > + }
> > > +
> > > + stl_le_p((uint8_t *)cache_mem + offset, value);
> > > +}
> > > +
> > > static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > > unsigned size)
> > > {
> > > @@ -141,6 +212,9 @@ static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > > if (offset >= A_CXL_HDM_DECODER_CAPABILITY &&
> > > offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) {
> > > dumb_hdm_handler(cxl_cstate, offset, value);
> > > + } else if (offset == A_CXL_BI_RT_CTRL ||
> > > + offset == A_CXL_BI_DECODER_CTRL) {
> > > + bi_handler(cxl_cstate, offset, value);
> > > } else {
> > > cregs->cache_mem_registers[offset / 4] = value;
> > > }
> > > @@ -230,7 +304,7 @@ static void ras_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > > }
> > >
> > > static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > - enum reg_type type)
> > > + enum reg_type type, bool bi)
> > > {
> > > int decoder_count = CXL_HDM_DECODER_COUNT;
> > > int hdm_inc = R_CXL_HDM_DECODER1_BASE_LO - R_CXL_HDM_DECODER0_BASE_LO;
> > > @@ -255,7 +329,9 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > UIO_DECODER_COUNT, 0);
> > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, MEMDATA_NXM_CAP, 0);
> > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY,
> > > - SUPPORTED_COHERENCY_MODEL, 0); /* Unknown */
> > > + SUPPORTED_COHERENCY_MODEL,
> > > + /* host+dev or Unknown */
> > > + type == CXL2_TYPE3_DEVICE && bi ? 3 : 0);
> > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_GLOBAL_CONTROL,
> > > HDM_DECODER_ENABLE, 0);
> > > write_msk[R_CXL_HDM_DECODER_GLOBAL_CONTROL] = 0x3;
> > > @@ -278,9 +354,43 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > }
> > > }
> > >
> > > +static void bi_rt_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > > +{
> > > + /* switch usp must commit the new BI-ID, timeout of 2secs */
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 1);
> > > +
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CTRL, COMMIT, 0);
> > > + write_msk[R_CXL_BI_RT_CTRL] = 0x1;
> > > +
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMITTED, 0);
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 0);
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 0x6);
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 0x2);
> > > +}
> > > +
> > > +static void bi_decoder_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > + enum reg_type type)
> > > +{
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, HDM_D, 0);
> > > + /* switch dsp must commit the new BI-ID, timeout of 2secs */
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT,
> > > + (type != CXL2_ROOT_PORT && type != CXL2_TYPE3_DEVICE));
> > > +
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_FW, 0);
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_ENABLE, 0);
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, COMMIT, 0);
> > > + write_msk[R_CXL_BI_DECODER_CTRL] = 0x7;
> > > +
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 0);
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 0x6);
> > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 0x2);
> > > +}
> > > +
> > > void cxl_component_register_init_common(uint32_t *reg_state,
> > > uint32_t *write_msk,
> > > - enum reg_type type)
> > > + enum reg_type type,
> > > + bool bi)
> > > {
> > > int caps = 0;
> > >
> > > @@ -320,7 +430,7 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > > case CXL2_LOGICAL_DEVICE:
> > > /* + HDM */
> > > init_cap_reg(HDM, 5, 1);
> > > - hdm_init_common(reg_state, write_msk, type);
> > > + hdm_init_common(reg_state, write_msk, type, bi);
> > > /* fallthrough */
> > > case CXL2_DOWNSTREAM_PORT:
> > > case CXL2_DEVICE:
> > > @@ -335,6 +445,24 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > > abort();
> > > }
> > >
> > > + /* back invalidate */
> > > + if (bi) {
> > > + switch (type) {
> > > + case CXL2_UPSTREAM_PORT:
> > > + init_cap_reg(BI_RT, 11, CXL_BI_RT_CAP_VERSION);
> > > + bi_rt_init_common(reg_state, write_msk);
> > > + break;
> > > + case CXL2_ROOT_PORT:
> > > + case CXL2_DOWNSTREAM_PORT:
> > > + case CXL2_TYPE3_DEVICE:
> > > + init_cap_reg(BI_DECODER, 12, CXL_BI_DECODER_CAP_VERSION);
> > > + bi_decoder_init_common(reg_state, write_msk, type);
> > > + break;
> > > + default:
> > > + break;
> > > + }
> > > + }
> > > +
> > > ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, ARRAY_SIZE, caps);
> > > #undef init_cap_reg
> > > }
> > > diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
> > > index 3c7ecd8c48bc..3f09c589ae58 100644
> > > --- a/hw/mem/cxl_type3.c
> > > +++ b/hw/mem/cxl_type3.c
> > > @@ -748,6 +748,11 @@ static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
> > > return false;
> > > }
> > >
> > > + if (!ct3d->flitmode && ct3d->hdmdb) {
> > > + error_setg(errp, "hdm-db requires operating in 256b flit");
> > > + return false;
> > > + }
> > > +
> > > if (ct3d->hostvmem) {
> > > MemoryRegion *vmr;
> > > char *v_name;
> > > @@ -1317,7 +1322,8 @@ static void ct3d_reset(DeviceState *dev)
> > >
> > > pcie_cap_fill_link_ep_usp(PCI_DEVICE(dev), ct3d->width, ct3d->speed,
> > > ct3d->flitmode);
> > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_TYPE3_DEVICE);
> > > + cxl_component_register_init_common(reg_state, write_msk,
> > > + CXL2_TYPE3_DEVICE, ct3d->hdmdb);
> > > cxl_device_register_init_t3(ct3d, CXL_T3_MSIX_MBOX);
> > >
> > > /*
> > > @@ -1356,6 +1362,7 @@ static const Property ct3_props[] = {
> > > DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLType3Dev,
> > > width, PCIE_LINK_WIDTH_16),
> > > DEFINE_PROP_BOOL("x-256b-flit", CXLType3Dev, flitmode, false),
> > > + DEFINE_PROP_BOOL("hdm-db", CXLType3Dev, hdmdb, false),
> > > };
> > >
> > > static uint64_t get_lsa_size(CXLType3Dev *ct3d)
> > > diff --git a/hw/pci-bridge/cxl_downstream.c b/hw/pci-bridge/cxl_downstream.c
> > > index 64086d8ec2f2..320818a8f1ce 100644
> > > --- a/hw/pci-bridge/cxl_downstream.c
> > > +++ b/hw/pci-bridge/cxl_downstream.c
> > > @@ -39,7 +39,7 @@ static void latch_registers(CXLDownstreamPort *dsp)
> > > uint32_t *write_msk = dsp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > >
> > > cxl_component_register_init_common(reg_state, write_msk,
> > > - CXL2_DOWNSTREAM_PORT);
> > > + CXL2_DOWNSTREAM_PORT, true);
> > > }
> > >
> > > /* TODO: Look at sharing this code across all CXL port types */
> > > diff --git a/hw/pci-bridge/cxl_root_port.c b/hw/pci-bridge/cxl_root_port.c
> > > index 5641048084a4..e2093ac39ee6 100644
> > > --- a/hw/pci-bridge/cxl_root_port.c
> > > +++ b/hw/pci-bridge/cxl_root_port.c
> > > @@ -101,7 +101,8 @@ static void latch_registers(CXLRootPort *crp)
> > > uint32_t *reg_state = crp->cxl_cstate.crb.cache_mem_registers;
> > > uint32_t *write_msk = crp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > >
> > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT);
> > > + cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT,
> > > + true);
> > > }
> > >
> > > static void build_dvsecs(PCIDevice *d, CXLComponentState *cxl)
> > > diff --git a/hw/pci-bridge/cxl_upstream.c b/hw/pci-bridge/cxl_upstream.c
> > > index c352d11dc7b7..fb8d19539c9f 100644
> > > --- a/hw/pci-bridge/cxl_upstream.c
> > > +++ b/hw/pci-bridge/cxl_upstream.c
> > > @@ -90,7 +90,7 @@ static void latch_registers(CXLUpstreamPort *usp)
> > > uint32_t *write_msk = usp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > >
> > > cxl_component_register_init_common(reg_state, write_msk,
> > > - CXL2_UPSTREAM_PORT);
> > > + CXL2_UPSTREAM_PORT, usp->flitmode);
> > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, TARGET_COUNT, 8);
> > > }
> > >
> > > diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
> > > index b6e2eb796951..11623a5666f6 100644
> > > --- a/hw/pci-bridge/pci_expander_bridge.c
> > > +++ b/hw/pci-bridge/pci_expander_bridge.c
> > > @@ -300,7 +300,7 @@ static void pxb_cxl_dev_reset(DeviceState *dev)
> > > uint32_t *write_msk = cxl_cstate->crb.cache_mem_regs_write_mask;
> > > int dsp_count = 0;
> > >
> > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_RC);
> > > + cxl_component_register_init_common(reg_state, write_msk, CXL2_RC, false);
> > > /*
> > > * The CXL specification allows for host bridges with no HDM decoders
> > > * if they only have a single root port.
> > > --
> > > 2.51.0
>
>
On Wed, Feb 04, 2026 at 03:21:02PM +0000, Jonathan Cameron wrote:
> On Wed, 4 Feb 2026 08:44:42 -0500
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
>
> > On Wed, Feb 04, 2026 at 08:24:55AM -0500, Michael S. Tsirkin wrote:
> > > On Wed, Feb 04, 2026 at 12:12:14PM +0000, Jonathan Cameron wrote:
> > > > From: Davidlohr Bueso <dave@stgolabs.net>
> > > >
> > > > Add basic plumbing for memory expander devices that support Back
> > > > Invalidation. This introduces a 'hdm-db=on|off' parameter and
> > > > exposes the relevant BI RT/Decoder component cachemem registers.
> > > >
> > > > Some noteworthy properties:
> > > > - Devices require enabling Flit mode across the CXL topology.
> > > > - Explicit BI-ID commit is required.
> > > > - HDM decoder support both host and dev coherency models.
> > > >
> > > > Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
> > > > Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> > > > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > >
> > > more troubles:
> > > https://gitlab.com/mstredhat/qemu/-/jobs/12984846000
> >
> >
> > clang just as unhappy:
> >
> > https://gitlab.com/mstredhat/qemu/-/jobs/12984846060
> They both seem to be clang.
>
> Replicated.
>
> Ah. This old gotcha - at one point I got one of my compiler colleagues to report
> it as a clang bug but he lost the argument vs the spec. Though I believe
> it is being fixed in the C spec longer term.
Yes the compiler actually says it's been fixed in C23.
> I can't find the thread
> now but we did discuss adding local scope in the macro a while back.
>
> Anyhow work around is to add scope to avoid label for the case statement
> being followed by _Static_assert()
> Despite smelling like a function, it's not and has special rules...
>
> Would you like a v7 or squash the following in?
> Thanks
>
> Jonathan
v7 pls.
>
> diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> index a3077184e230..07aabe331c44 100644
> --- a/hw/cxl/cxl-component-utils.c
> +++ b/hw/cxl/cxl-component-utils.c
> @@ -68,7 +68,7 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> ComponentRegisters *cregs = &cxl_cstate->crb;
>
> switch (size) {
> - case 4:
> + case 4: {
> QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
>
> if (offset == A_CXL_BI_RT_STATUS ||
> @@ -101,6 +101,7 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> }
>
> return cregs->cache_mem_registers[offset / 4];
> + }
> case 8:
> qemu_log_mask(LOG_UNIMP,
> "CXL 8 byte cache mem registers not implemented\n");
>
>
> >
> > >
> > > > ---
> > > > v6: Initialize type variable to avoid a false compiler warning
> > > > from some versions of gcc. (Michael Tsirkin)
> > > > ---
> > > > docs/system/devices/cxl.rst | 23 +++++
> > > > include/hw/cxl/cxl_component.h | 54 ++++++++++-
> > > > include/hw/cxl/cxl_device.h | 3 +
> > > > hw/cxl/cxl-component-utils.c | 142 ++++++++++++++++++++++++++--
> > > > hw/mem/cxl_type3.c | 9 +-
> > > > hw/pci-bridge/cxl_downstream.c | 2 +-
> > > > hw/pci-bridge/cxl_root_port.c | 3 +-
> > > > hw/pci-bridge/cxl_upstream.c | 2 +-
> > > > hw/pci-bridge/pci_expander_bridge.c | 2 +-
> > > > 9 files changed, 225 insertions(+), 15 deletions(-)
> > > >
> > > > diff --git a/docs/system/devices/cxl.rst b/docs/system/devices/cxl.rst
> > > > index ca15a0da1c1d..9d0771cdfd73 100644
> > > > --- a/docs/system/devices/cxl.rst
> > > > +++ b/docs/system/devices/cxl.rst
> > > > @@ -384,6 +384,29 @@ An example of 4 devices below a switch suitable for 1, 2 or 4 way interleave::
> > > > -device cxl-type3,bus=swport3,persistent-memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem3,sn=0x4 \
> > > > -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > > >
> > > > +An example of 4 type3 devices with volatile memory below a switch. Two of the devices
> > > > +use HDM-DB for coherence, which requires operating in Flit mode::
> > > > +
> > > > + qemu-system-x86_64 -M q35,cxl=on -m 4G,maxmem=8G,slots=8 -smp 4 \
> > > > + ...
> > > > + -object memory-backend-ram,id=cxl-mem0,share=on,size=256M \
> > > > + -object memory-backend-ram,id=cxl-mem1,share=on,size=256M \
> > > > + -object memory-backend-ram,id=cxl-mem2,share=on,size=256M \
> > > > + -object memory-backend-ram,id=cxl-mem3,share=on,size=256M \
> > > > + -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
> > > > + -device cxl-rp,port=0,bus=cxl.1,id=root_port0,chassis=0,slot=0 \
> > > > + -device cxl-rp,port=1,bus=cxl.1,id=root_port1,chassis=0,slot=1 \
> > > > + -device cxl-upstream,bus=root_port0,id=us0,x-256b-flit=on \
> > > > + -device cxl-downstream,port=0,bus=us0,id=swport0,chassis=0,slot=4 \
> > > > + -device cxl-type3,bus=swport0,volatile-memdev=cxl-mem0,id=cxl-mem0,sn=0x1,x-256b-flit=on,hdm-db=on \
> > > > + -device cxl-downstream,port=1,bus=us0,id=swport1,chassis=0,slot=5 \
> > > > + -device cxl-type3,bus=swport1,volatile-memdev=cxl-mem1,id=cxl-mem1,sn=0x2,x-256b-flit=on,hdm-db=on \
> > > > + -device cxl-downstream,port=2,bus=us0,id=swport2,chassis=0,slot=6 \
> > > > + -device cxl-type3,bus=swport2,volatile-memdev=cxl-mem2,id=cxl-mem2,sn=0x3 \
> > > > + -device cxl-downstream,port=3,bus=us0,id=swport3,chassis=0,slot=7 \
> > > > + -device cxl-type3,bus=swport3,volatile-memdev=cxl-mem3,id=cxl-mem3,sn=0x4 \
> > > > + -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > > > +
> > > > A simple arm/virt example featuring a single direct connected CXL Type 3
> > > > Volatile Memory device::
> > > >
> > > > diff --git a/include/hw/cxl/cxl_component.h b/include/hw/cxl/cxl_component.h
> > > > index 1f167d3ef79b..ffc82202206c 100644
> > > > --- a/include/hw/cxl/cxl_component.h
> > > > +++ b/include/hw/cxl/cxl_component.h
> > > > @@ -67,6 +67,8 @@ CXLx_CAPABILITY_HEADER(LINK, 2)
> > > > CXLx_CAPABILITY_HEADER(HDM, 3)
> > > > CXLx_CAPABILITY_HEADER(EXTSEC, 4)
> > > > CXLx_CAPABILITY_HEADER(SNOOP, 5)
> > > > +CXLx_CAPABILITY_HEADER(BI_RT, 6)
> > > > +CXLx_CAPABILITY_HEADER(BI_DECODER, 7)
> > > >
> > > > /*
> > > > * Capability structures contain the actual registers that the CXL component
> > > > @@ -211,10 +213,55 @@ HDM_DECODER_INIT(3);
> > > > (CXL_IDE_REGISTERS_OFFSET + CXL_IDE_REGISTERS_SIZE)
> > > > #define CXL_SNOOP_REGISTERS_SIZE 0x8
> > > >
> > > > -QEMU_BUILD_BUG_MSG((CXL_SNOOP_REGISTERS_OFFSET +
> > > > - CXL_SNOOP_REGISTERS_SIZE) >= 0x1000,
> > > > +#define CXL_BI_RT_CAP_VERSION 1
> > > > +#define CXL_BI_RT_REGISTERS_OFFSET \
> > > > + (CXL_SNOOP_REGISTERS_OFFSET + CXL_SNOOP_REGISTERS_SIZE)
> > > > +#define CXL_BI_RT_REGISTERS_SIZE 0xC
> > > > +
> > > > +REG32(CXL_BI_RT_CAPABILITY, CXL_BI_RT_REGISTERS_OFFSET)
> > > > + FIELD(CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 0, 1)
> > > > +REG32(CXL_BI_RT_CTRL, CXL_BI_RT_REGISTERS_OFFSET + 0x4)
> > > > + FIELD(CXL_BI_RT_CTRL, COMMIT, 0, 1)
> > > > +REG32(CXL_BI_RT_STATUS, CXL_BI_RT_REGISTERS_OFFSET + 0x8)
> > > > + FIELD(CXL_BI_RT_STATUS, COMMITTED, 0, 1)
> > > > + FIELD(CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > > > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > > > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 12, 4)
> > > > +
> > > > +/* CXL r3.2 8.2.4.27 - CXL BI Decoder Capability Structure */
> > > > +#define CXL_BI_DECODER_CAP_VERSION 1
> > > > +#define CXL_BI_DECODER_REGISTERS_OFFSET \
> > > > + (CXL_BI_RT_REGISTERS_OFFSET + CXL_BI_RT_REGISTERS_SIZE)
> > > > +#define CXL_BI_DECODER_REGISTERS_SIZE 0xC
> > > > +
> > > > +REG32(CXL_BI_DECODER_CAPABILITY, CXL_BI_DECODER_REGISTERS_OFFSET)
> > > > + FIELD(CXL_BI_DECODER_CAPABILITY, HDM_D, 0, 1)
> > > > + FIELD(CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT, 1, 1)
> > > > +REG32(CXL_BI_DECODER_CTRL, CXL_BI_DECODER_REGISTERS_OFFSET + 0x4)
> > > > + FIELD(CXL_BI_DECODER_CTRL, BI_FW, 0, 1)
> > > > + FIELD(CXL_BI_DECODER_CTRL, BI_ENABLE, 1, 1)
> > > > + FIELD(CXL_BI_DECODER_CTRL, COMMIT, 2, 1)
> > > > +REG32(CXL_BI_DECODER_STATUS, CXL_BI_DECODER_REGISTERS_OFFSET + 0x8)
> > > > + FIELD(CXL_BI_DECODER_STATUS, COMMITTED, 0, 1)
> > > > + FIELD(CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > > > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > > > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 12, 4)
> > > > +
> > > > +QEMU_BUILD_BUG_MSG((CXL_BI_DECODER_REGISTERS_OFFSET +
> > > > + CXL_BI_DECODER_REGISTERS_SIZE) >= 0x1000,
> > > > "No space for registers");
> > > >
> > > > +/* track BI explicit commit handling for route table and decoder */
> > > > +enum {
> > > > + CXL_BISTATE_RT = 0,
> > > > + CXL_BISTATE_DECODER,
> > > > + CXL_BISTATE_MAX
> > > > +};
> > > > +
> > > > +typedef struct bi_state {
> > > > + uint64_t last_commit; /* last 0->1 transition */
> > > > +} BIState;
> > > > +
> > > > typedef struct component_registers {
> > > > /*
> > > > * Main memory region to be registered with QEMU core.
> > > > @@ -259,6 +306,7 @@ typedef struct cxl_component {
> > > > };
> > > >
> > > > CDATObject cdat;
> > > > + BIState bi_state[CXL_BISTATE_MAX];
> > > > } CXLComponentState;
> > > >
> > > > void cxl_component_register_block_init(Object *obj,
> > > > @@ -266,7 +314,7 @@ void cxl_component_register_block_init(Object *obj,
> > > > const char *type);
> > > > void cxl_component_register_init_common(uint32_t *reg_state,
> > > > uint32_t *write_msk,
> > > > - enum reg_type type);
> > > > + enum reg_type type, bool bi);
> > > >
> > > > void cxl_component_create_dvsec(CXLComponentState *cxl_cstate,
> > > > enum reg_type cxl_dev_type, uint16_t length,
> > > > diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
> > > > index 7d9236db8c85..393f3122173b 100644
> > > > --- a/include/hw/cxl/cxl_device.h
> > > > +++ b/include/hw/cxl/cxl_device.h
> > > > @@ -770,6 +770,9 @@ struct CXLType3Dev {
> > > > CXLMemSparingReadAttrs rank_sparing_attrs;
> > > > CXLMemSparingWriteAttrs rank_sparing_wr_attrs;
> > > >
> > > > + /* BI flows */
> > > > + bool hdmdb;
> > > > +
> > > > struct dynamic_capacity {
> > > > HostMemoryBackend *host_dc;
> > > > AddressSpace host_dc_as;
> > > > diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> > > > index 91770f103a85..a7d36e1128c2 100644
> > > > --- a/hw/cxl/cxl-component-utils.c
> > > > +++ b/hw/cxl/cxl-component-utils.c
> > > > @@ -71,10 +71,40 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> > > > case 4:
> > > > if (cregs->special_ops && cregs->special_ops->read) {
> > > > return cregs->special_ops->read(cxl_cstate, offset, 4);
> > > > - } else {
> > > > - QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > > > - return cregs->cache_mem_registers[offset / 4];
> > > > }
> > > > +
> > > > + QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > > > +
> > > > + if (offset == A_CXL_BI_RT_STATUS ||
> > > > + offset == A_CXL_BI_DECODER_STATUS) {
> > > > + int type;
> > > > + uint64_t started;
> > > > +
> > > > + type = (offset == A_CXL_BI_RT_STATUS) ?
> > > > + CXL_BISTATE_RT : CXL_BISTATE_DECODER;
> > > > + started = cxl_cstate->bi_state[type].last_commit;
> > > > +
> > > > + if (started) {
> > > > + uint32_t *cache_mem = cregs->cache_mem_registers;
> > > > + uint32_t val = cache_mem[offset / 4];
> > > > + uint64_t now;
> > > > + int set;
> > > > +
> > > > + now = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > > > + /* arbitrary 100 ms to do the commit */
> > > > + set = !!(now >= started + 100);
> > > > +
> > > > + if (offset == A_CXL_BI_RT_STATUS) {
> > > > + val = FIELD_DP32(val, CXL_BI_RT_STATUS, COMMITTED, set);
> > > > + } else {
> > > > + val = FIELD_DP32(val, CXL_BI_DECODER_STATUS, COMMITTED,
> > > > + set);
> > > > + }
> > > > + stl_le_p((uint8_t *)cache_mem + offset, val);
> > > > + }
> > > > + }
> > > > +
> > > > + return cregs->cache_mem_registers[offset / 4];
> > > > case 8:
> > > > qemu_log_mask(LOG_UNIMP,
> > > > "CXL 8 byte cache mem registers not implemented\n");
> > > > @@ -118,6 +148,47 @@ static void dumb_hdm_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > > > stl_le_p((uint8_t *)cache_mem + offset, value);
> > > > }
> > > >
> > > > +static void bi_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > > > + uint32_t value)
> > > > +{
> > > > + ComponentRegisters *cregs = &cxl_cstate->crb;
> > > > + uint32_t sts, *cache_mem = cregs->cache_mem_registers;
> > > > + bool to_commit = false;
> > > > + int type = 0; /* Unused value - work around for compiler warning */
> > > > +
> > > > + switch (offset) {
> > > > + case A_CXL_BI_RT_CTRL:
> > > > + to_commit = FIELD_EX32(value, CXL_BI_RT_CTRL, COMMIT);
> > > > + if (to_commit) {
> > > > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > > > + R_CXL_BI_RT_STATUS, 4);
> > > > + sts = FIELD_DP32(sts, CXL_BI_RT_STATUS, COMMITTED, 0);
> > > > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_RT_STATUS, sts);
> > > > + type = CXL_BISTATE_RT;
> > > > + }
> > > > + break;
> > > > + case A_CXL_BI_DECODER_CTRL:
> > > > + to_commit = FIELD_EX32(value, CXL_BI_DECODER_CTRL, COMMIT);
> > > > + if (to_commit) {
> > > > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > > > + R_CXL_BI_DECODER_STATUS, 4);
> > > > + sts = FIELD_DP32(sts, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > > > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_DECODER_STATUS, sts);
> > > > + type = CXL_BISTATE_DECODER;
> > > > + }
> > > > + break;
> > > > + default:
> > > > + break;
> > > > + }
> > > > +
> > > > + if (to_commit) {
> > > > + cxl_cstate->bi_state[type].last_commit =
> > > > + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > > > + }
> > > > +
> > > > + stl_le_p((uint8_t *)cache_mem + offset, value);
> > > > +}
> > > > +
> > > > static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > > > unsigned size)
> > > > {
> > > > @@ -141,6 +212,9 @@ static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > > > if (offset >= A_CXL_HDM_DECODER_CAPABILITY &&
> > > > offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) {
> > > > dumb_hdm_handler(cxl_cstate, offset, value);
> > > > + } else if (offset == A_CXL_BI_RT_CTRL ||
> > > > + offset == A_CXL_BI_DECODER_CTRL) {
> > > > + bi_handler(cxl_cstate, offset, value);
> > > > } else {
> > > > cregs->cache_mem_registers[offset / 4] = value;
> > > > }
> > > > @@ -230,7 +304,7 @@ static void ras_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > > > }
> > > >
> > > > static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > - enum reg_type type)
> > > > + enum reg_type type, bool bi)
> > > > {
> > > > int decoder_count = CXL_HDM_DECODER_COUNT;
> > > > int hdm_inc = R_CXL_HDM_DECODER1_BASE_LO - R_CXL_HDM_DECODER0_BASE_LO;
> > > > @@ -255,7 +329,9 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > UIO_DECODER_COUNT, 0);
> > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, MEMDATA_NXM_CAP, 0);
> > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY,
> > > > - SUPPORTED_COHERENCY_MODEL, 0); /* Unknown */
> > > > + SUPPORTED_COHERENCY_MODEL,
> > > > + /* host+dev or Unknown */
> > > > + type == CXL2_TYPE3_DEVICE && bi ? 3 : 0);
> > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_GLOBAL_CONTROL,
> > > > HDM_DECODER_ENABLE, 0);
> > > > write_msk[R_CXL_HDM_DECODER_GLOBAL_CONTROL] = 0x3;
> > > > @@ -278,9 +354,43 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > }
> > > > }
> > > >
> > > > +static void bi_rt_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > > > +{
> > > > + /* switch usp must commit the new BI-ID, timeout of 2secs */
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 1);
> > > > +
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CTRL, COMMIT, 0);
> > > > + write_msk[R_CXL_BI_RT_CTRL] = 0x1;
> > > > +
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMITTED, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 0x6);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 0x2);
> > > > +}
> > > > +
> > > > +static void bi_decoder_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > + enum reg_type type)
> > > > +{
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, HDM_D, 0);
> > > > + /* switch dsp must commit the new BI-ID, timeout of 2secs */
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT,
> > > > + (type != CXL2_ROOT_PORT && type != CXL2_TYPE3_DEVICE));
> > > > +
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_FW, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_ENABLE, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, COMMIT, 0);
> > > > + write_msk[R_CXL_BI_DECODER_CTRL] = 0x7;
> > > > +
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 0x6);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 0x2);
> > > > +}
> > > > +
> > > > void cxl_component_register_init_common(uint32_t *reg_state,
> > > > uint32_t *write_msk,
> > > > - enum reg_type type)
> > > > + enum reg_type type,
> > > > + bool bi)
> > > > {
> > > > int caps = 0;
> > > >
> > > > @@ -320,7 +430,7 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > > > case CXL2_LOGICAL_DEVICE:
> > > > /* + HDM */
> > > > init_cap_reg(HDM, 5, 1);
> > > > - hdm_init_common(reg_state, write_msk, type);
> > > > + hdm_init_common(reg_state, write_msk, type, bi);
> > > > /* fallthrough */
> > > > case CXL2_DOWNSTREAM_PORT:
> > > > case CXL2_DEVICE:
> > > > @@ -335,6 +445,24 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > > > abort();
> > > > }
> > > >
> > > > + /* back invalidate */
> > > > + if (bi) {
> > > > + switch (type) {
> > > > + case CXL2_UPSTREAM_PORT:
> > > > + init_cap_reg(BI_RT, 11, CXL_BI_RT_CAP_VERSION);
> > > > + bi_rt_init_common(reg_state, write_msk);
> > > > + break;
> > > > + case CXL2_ROOT_PORT:
> > > > + case CXL2_DOWNSTREAM_PORT:
> > > > + case CXL2_TYPE3_DEVICE:
> > > > + init_cap_reg(BI_DECODER, 12, CXL_BI_DECODER_CAP_VERSION);
> > > > + bi_decoder_init_common(reg_state, write_msk, type);
> > > > + break;
> > > > + default:
> > > > + break;
> > > > + }
> > > > + }
> > > > +
> > > > ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, ARRAY_SIZE, caps);
> > > > #undef init_cap_reg
> > > > }
> > > > diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
> > > > index 3c7ecd8c48bc..3f09c589ae58 100644
> > > > --- a/hw/mem/cxl_type3.c
> > > > +++ b/hw/mem/cxl_type3.c
> > > > @@ -748,6 +748,11 @@ static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
> > > > return false;
> > > > }
> > > >
> > > > + if (!ct3d->flitmode && ct3d->hdmdb) {
> > > > + error_setg(errp, "hdm-db requires operating in 256b flit");
> > > > + return false;
> > > > + }
> > > > +
> > > > if (ct3d->hostvmem) {
> > > > MemoryRegion *vmr;
> > > > char *v_name;
> > > > @@ -1317,7 +1322,8 @@ static void ct3d_reset(DeviceState *dev)
> > > >
> > > > pcie_cap_fill_link_ep_usp(PCI_DEVICE(dev), ct3d->width, ct3d->speed,
> > > > ct3d->flitmode);
> > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_TYPE3_DEVICE);
> > > > + cxl_component_register_init_common(reg_state, write_msk,
> > > > + CXL2_TYPE3_DEVICE, ct3d->hdmdb);
> > > > cxl_device_register_init_t3(ct3d, CXL_T3_MSIX_MBOX);
> > > >
> > > > /*
> > > > @@ -1356,6 +1362,7 @@ static const Property ct3_props[] = {
> > > > DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLType3Dev,
> > > > width, PCIE_LINK_WIDTH_16),
> > > > DEFINE_PROP_BOOL("x-256b-flit", CXLType3Dev, flitmode, false),
> > > > + DEFINE_PROP_BOOL("hdm-db", CXLType3Dev, hdmdb, false),
> > > > };
> > > >
> > > > static uint64_t get_lsa_size(CXLType3Dev *ct3d)
> > > > diff --git a/hw/pci-bridge/cxl_downstream.c b/hw/pci-bridge/cxl_downstream.c
> > > > index 64086d8ec2f2..320818a8f1ce 100644
> > > > --- a/hw/pci-bridge/cxl_downstream.c
> > > > +++ b/hw/pci-bridge/cxl_downstream.c
> > > > @@ -39,7 +39,7 @@ static void latch_registers(CXLDownstreamPort *dsp)
> > > > uint32_t *write_msk = dsp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > >
> > > > cxl_component_register_init_common(reg_state, write_msk,
> > > > - CXL2_DOWNSTREAM_PORT);
> > > > + CXL2_DOWNSTREAM_PORT, true);
> > > > }
> > > >
> > > > /* TODO: Look at sharing this code across all CXL port types */
> > > > diff --git a/hw/pci-bridge/cxl_root_port.c b/hw/pci-bridge/cxl_root_port.c
> > > > index 5641048084a4..e2093ac39ee6 100644
> > > > --- a/hw/pci-bridge/cxl_root_port.c
> > > > +++ b/hw/pci-bridge/cxl_root_port.c
> > > > @@ -101,7 +101,8 @@ static void latch_registers(CXLRootPort *crp)
> > > > uint32_t *reg_state = crp->cxl_cstate.crb.cache_mem_registers;
> > > > uint32_t *write_msk = crp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > >
> > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT);
> > > > + cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT,
> > > > + true);
> > > > }
> > > >
> > > > static void build_dvsecs(PCIDevice *d, CXLComponentState *cxl)
> > > > diff --git a/hw/pci-bridge/cxl_upstream.c b/hw/pci-bridge/cxl_upstream.c
> > > > index c352d11dc7b7..fb8d19539c9f 100644
> > > > --- a/hw/pci-bridge/cxl_upstream.c
> > > > +++ b/hw/pci-bridge/cxl_upstream.c
> > > > @@ -90,7 +90,7 @@ static void latch_registers(CXLUpstreamPort *usp)
> > > > uint32_t *write_msk = usp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > >
> > > > cxl_component_register_init_common(reg_state, write_msk,
> > > > - CXL2_UPSTREAM_PORT);
> > > > + CXL2_UPSTREAM_PORT, usp->flitmode);
> > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, TARGET_COUNT, 8);
> > > > }
> > > >
> > > > diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
> > > > index b6e2eb796951..11623a5666f6 100644
> > > > --- a/hw/pci-bridge/pci_expander_bridge.c
> > > > +++ b/hw/pci-bridge/pci_expander_bridge.c
> > > > @@ -300,7 +300,7 @@ static void pxb_cxl_dev_reset(DeviceState *dev)
> > > > uint32_t *write_msk = cxl_cstate->crb.cache_mem_regs_write_mask;
> > > > int dsp_count = 0;
> > > >
> > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_RC);
> > > > + cxl_component_register_init_common(reg_state, write_msk, CXL2_RC, false);
> > > > /*
> > > > * The CXL specification allows for host bridges with no HDM decoders
> > > > * if they only have a single root port.
> > > > --
> > > > 2.51.0
> >
> >
On Wed, 4 Feb 2026 15:21:02 +0000
Jonathan Cameron via qemu development <qemu-devel@nongnu.org> wrote:
> On Wed, 4 Feb 2026 08:44:42 -0500
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
>
> > On Wed, Feb 04, 2026 at 08:24:55AM -0500, Michael S. Tsirkin wrote:
> > > On Wed, Feb 04, 2026 at 12:12:14PM +0000, Jonathan Cameron wrote:
> > > > From: Davidlohr Bueso <dave@stgolabs.net>
> > > >
> > > > Add basic plumbing for memory expander devices that support Back
> > > > Invalidation. This introduces a 'hdm-db=on|off' parameter and
> > > > exposes the relevant BI RT/Decoder component cachemem registers.
> > > >
> > > > Some noteworthy properties:
> > > > - Devices require enabling Flit mode across the CXL topology.
> > > > - Explicit BI-ID commit is required.
> > > > - HDM decoder support both host and dev coherency models.
> > > >
> > > > Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
> > > > Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> > > > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > >
> > > more troubles:
> > > https://gitlab.com/mstredhat/qemu/-/jobs/12984846000
> >
> >
> > clang just as unhappy:
> >
> > https://gitlab.com/mstredhat/qemu/-/jobs/12984846060
> They both seem to be clang.
>
> Replicated.
>
> Ah. This old gotcha - at one point I got one of my compiler colleagues to report
> it as a clang bug but he lost the argument vs the spec. Though I believe
> it is being fixed in the C spec longer term. I can't find the thread
> now but we did discuss adding local scope in the macro a while back.
>
> Anyhow work around is to add scope to avoid label for the case statement
> being followed by _Static_assert()
> Despite smelling like a function, it's not and has special rules...
>
> Would you like a v7 or squash the following in?
Or. The problem only actually occurs after the next patch (which happens
to bring the _static assert to the top of the case statement.)
So drop patch 7 and I'll revisit just that little one at a later date.
> Thanks
>
> Jonathan
>
>
> diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> index a3077184e230..07aabe331c44 100644
> --- a/hw/cxl/cxl-component-utils.c
> +++ b/hw/cxl/cxl-component-utils.c
> @@ -68,7 +68,7 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> ComponentRegisters *cregs = &cxl_cstate->crb;
>
> switch (size) {
> - case 4:
> + case 4: {
> QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
>
> if (offset == A_CXL_BI_RT_STATUS ||
> @@ -101,6 +101,7 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> }
>
> return cregs->cache_mem_registers[offset / 4];
> + }
> case 8:
> qemu_log_mask(LOG_UNIMP,
> "CXL 8 byte cache mem registers not implemented\n");
>
>
> >
> > >
> > > > ---
> > > > v6: Initialize type variable to avoid a false compiler warning
> > > > from some versions of gcc. (Michael Tsirkin)
> > > > ---
> > > > docs/system/devices/cxl.rst | 23 +++++
> > > > include/hw/cxl/cxl_component.h | 54 ++++++++++-
> > > > include/hw/cxl/cxl_device.h | 3 +
> > > > hw/cxl/cxl-component-utils.c | 142 ++++++++++++++++++++++++++--
> > > > hw/mem/cxl_type3.c | 9 +-
> > > > hw/pci-bridge/cxl_downstream.c | 2 +-
> > > > hw/pci-bridge/cxl_root_port.c | 3 +-
> > > > hw/pci-bridge/cxl_upstream.c | 2 +-
> > > > hw/pci-bridge/pci_expander_bridge.c | 2 +-
> > > > 9 files changed, 225 insertions(+), 15 deletions(-)
> > > >
> > > > diff --git a/docs/system/devices/cxl.rst b/docs/system/devices/cxl.rst
> > > > index ca15a0da1c1d..9d0771cdfd73 100644
> > > > --- a/docs/system/devices/cxl.rst
> > > > +++ b/docs/system/devices/cxl.rst
> > > > @@ -384,6 +384,29 @@ An example of 4 devices below a switch suitable for 1, 2 or 4 way interleave::
> > > > -device cxl-type3,bus=swport3,persistent-memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem3,sn=0x4 \
> > > > -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > > >
> > > > +An example of 4 type3 devices with volatile memory below a switch. Two of the devices
> > > > +use HDM-DB for coherence, which requires operating in Flit mode::
> > > > +
> > > > + qemu-system-x86_64 -M q35,cxl=on -m 4G,maxmem=8G,slots=8 -smp 4 \
> > > > + ...
> > > > + -object memory-backend-ram,id=cxl-mem0,share=on,size=256M \
> > > > + -object memory-backend-ram,id=cxl-mem1,share=on,size=256M \
> > > > + -object memory-backend-ram,id=cxl-mem2,share=on,size=256M \
> > > > + -object memory-backend-ram,id=cxl-mem3,share=on,size=256M \
> > > > + -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
> > > > + -device cxl-rp,port=0,bus=cxl.1,id=root_port0,chassis=0,slot=0 \
> > > > + -device cxl-rp,port=1,bus=cxl.1,id=root_port1,chassis=0,slot=1 \
> > > > + -device cxl-upstream,bus=root_port0,id=us0,x-256b-flit=on \
> > > > + -device cxl-downstream,port=0,bus=us0,id=swport0,chassis=0,slot=4 \
> > > > + -device cxl-type3,bus=swport0,volatile-memdev=cxl-mem0,id=cxl-mem0,sn=0x1,x-256b-flit=on,hdm-db=on \
> > > > + -device cxl-downstream,port=1,bus=us0,id=swport1,chassis=0,slot=5 \
> > > > + -device cxl-type3,bus=swport1,volatile-memdev=cxl-mem1,id=cxl-mem1,sn=0x2,x-256b-flit=on,hdm-db=on \
> > > > + -device cxl-downstream,port=2,bus=us0,id=swport2,chassis=0,slot=6 \
> > > > + -device cxl-type3,bus=swport2,volatile-memdev=cxl-mem2,id=cxl-mem2,sn=0x3 \
> > > > + -device cxl-downstream,port=3,bus=us0,id=swport3,chassis=0,slot=7 \
> > > > + -device cxl-type3,bus=swport3,volatile-memdev=cxl-mem3,id=cxl-mem3,sn=0x4 \
> > > > + -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > > > +
> > > > A simple arm/virt example featuring a single direct connected CXL Type 3
> > > > Volatile Memory device::
> > > >
> > > > diff --git a/include/hw/cxl/cxl_component.h b/include/hw/cxl/cxl_component.h
> > > > index 1f167d3ef79b..ffc82202206c 100644
> > > > --- a/include/hw/cxl/cxl_component.h
> > > > +++ b/include/hw/cxl/cxl_component.h
> > > > @@ -67,6 +67,8 @@ CXLx_CAPABILITY_HEADER(LINK, 2)
> > > > CXLx_CAPABILITY_HEADER(HDM, 3)
> > > > CXLx_CAPABILITY_HEADER(EXTSEC, 4)
> > > > CXLx_CAPABILITY_HEADER(SNOOP, 5)
> > > > +CXLx_CAPABILITY_HEADER(BI_RT, 6)
> > > > +CXLx_CAPABILITY_HEADER(BI_DECODER, 7)
> > > >
> > > > /*
> > > > * Capability structures contain the actual registers that the CXL component
> > > > @@ -211,10 +213,55 @@ HDM_DECODER_INIT(3);
> > > > (CXL_IDE_REGISTERS_OFFSET + CXL_IDE_REGISTERS_SIZE)
> > > > #define CXL_SNOOP_REGISTERS_SIZE 0x8
> > > >
> > > > -QEMU_BUILD_BUG_MSG((CXL_SNOOP_REGISTERS_OFFSET +
> > > > - CXL_SNOOP_REGISTERS_SIZE) >= 0x1000,
> > > > +#define CXL_BI_RT_CAP_VERSION 1
> > > > +#define CXL_BI_RT_REGISTERS_OFFSET \
> > > > + (CXL_SNOOP_REGISTERS_OFFSET + CXL_SNOOP_REGISTERS_SIZE)
> > > > +#define CXL_BI_RT_REGISTERS_SIZE 0xC
> > > > +
> > > > +REG32(CXL_BI_RT_CAPABILITY, CXL_BI_RT_REGISTERS_OFFSET)
> > > > + FIELD(CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 0, 1)
> > > > +REG32(CXL_BI_RT_CTRL, CXL_BI_RT_REGISTERS_OFFSET + 0x4)
> > > > + FIELD(CXL_BI_RT_CTRL, COMMIT, 0, 1)
> > > > +REG32(CXL_BI_RT_STATUS, CXL_BI_RT_REGISTERS_OFFSET + 0x8)
> > > > + FIELD(CXL_BI_RT_STATUS, COMMITTED, 0, 1)
> > > > + FIELD(CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > > > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > > > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 12, 4)
> > > > +
> > > > +/* CXL r3.2 8.2.4.27 - CXL BI Decoder Capability Structure */
> > > > +#define CXL_BI_DECODER_CAP_VERSION 1
> > > > +#define CXL_BI_DECODER_REGISTERS_OFFSET \
> > > > + (CXL_BI_RT_REGISTERS_OFFSET + CXL_BI_RT_REGISTERS_SIZE)
> > > > +#define CXL_BI_DECODER_REGISTERS_SIZE 0xC
> > > > +
> > > > +REG32(CXL_BI_DECODER_CAPABILITY, CXL_BI_DECODER_REGISTERS_OFFSET)
> > > > + FIELD(CXL_BI_DECODER_CAPABILITY, HDM_D, 0, 1)
> > > > + FIELD(CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT, 1, 1)
> > > > +REG32(CXL_BI_DECODER_CTRL, CXL_BI_DECODER_REGISTERS_OFFSET + 0x4)
> > > > + FIELD(CXL_BI_DECODER_CTRL, BI_FW, 0, 1)
> > > > + FIELD(CXL_BI_DECODER_CTRL, BI_ENABLE, 1, 1)
> > > > + FIELD(CXL_BI_DECODER_CTRL, COMMIT, 2, 1)
> > > > +REG32(CXL_BI_DECODER_STATUS, CXL_BI_DECODER_REGISTERS_OFFSET + 0x8)
> > > > + FIELD(CXL_BI_DECODER_STATUS, COMMITTED, 0, 1)
> > > > + FIELD(CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > > > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > > > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 12, 4)
> > > > +
> > > > +QEMU_BUILD_BUG_MSG((CXL_BI_DECODER_REGISTERS_OFFSET +
> > > > + CXL_BI_DECODER_REGISTERS_SIZE) >= 0x1000,
> > > > "No space for registers");
> > > >
> > > > +/* track BI explicit commit handling for route table and decoder */
> > > > +enum {
> > > > + CXL_BISTATE_RT = 0,
> > > > + CXL_BISTATE_DECODER,
> > > > + CXL_BISTATE_MAX
> > > > +};
> > > > +
> > > > +typedef struct bi_state {
> > > > + uint64_t last_commit; /* last 0->1 transition */
> > > > +} BIState;
> > > > +
> > > > typedef struct component_registers {
> > > > /*
> > > > * Main memory region to be registered with QEMU core.
> > > > @@ -259,6 +306,7 @@ typedef struct cxl_component {
> > > > };
> > > >
> > > > CDATObject cdat;
> > > > + BIState bi_state[CXL_BISTATE_MAX];
> > > > } CXLComponentState;
> > > >
> > > > void cxl_component_register_block_init(Object *obj,
> > > > @@ -266,7 +314,7 @@ void cxl_component_register_block_init(Object *obj,
> > > > const char *type);
> > > > void cxl_component_register_init_common(uint32_t *reg_state,
> > > > uint32_t *write_msk,
> > > > - enum reg_type type);
> > > > + enum reg_type type, bool bi);
> > > >
> > > > void cxl_component_create_dvsec(CXLComponentState *cxl_cstate,
> > > > enum reg_type cxl_dev_type, uint16_t length,
> > > > diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
> > > > index 7d9236db8c85..393f3122173b 100644
> > > > --- a/include/hw/cxl/cxl_device.h
> > > > +++ b/include/hw/cxl/cxl_device.h
> > > > @@ -770,6 +770,9 @@ struct CXLType3Dev {
> > > > CXLMemSparingReadAttrs rank_sparing_attrs;
> > > > CXLMemSparingWriteAttrs rank_sparing_wr_attrs;
> > > >
> > > > + /* BI flows */
> > > > + bool hdmdb;
> > > > +
> > > > struct dynamic_capacity {
> > > > HostMemoryBackend *host_dc;
> > > > AddressSpace host_dc_as;
> > > > diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> > > > index 91770f103a85..a7d36e1128c2 100644
> > > > --- a/hw/cxl/cxl-component-utils.c
> > > > +++ b/hw/cxl/cxl-component-utils.c
> > > > @@ -71,10 +71,40 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> > > > case 4:
> > > > if (cregs->special_ops && cregs->special_ops->read) {
> > > > return cregs->special_ops->read(cxl_cstate, offset, 4);
> > > > - } else {
> > > > - QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > > > - return cregs->cache_mem_registers[offset / 4];
> > > > }
> > > > +
> > > > + QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > > > +
> > > > + if (offset == A_CXL_BI_RT_STATUS ||
> > > > + offset == A_CXL_BI_DECODER_STATUS) {
> > > > + int type;
> > > > + uint64_t started;
> > > > +
> > > > + type = (offset == A_CXL_BI_RT_STATUS) ?
> > > > + CXL_BISTATE_RT : CXL_BISTATE_DECODER;
> > > > + started = cxl_cstate->bi_state[type].last_commit;
> > > > +
> > > > + if (started) {
> > > > + uint32_t *cache_mem = cregs->cache_mem_registers;
> > > > + uint32_t val = cache_mem[offset / 4];
> > > > + uint64_t now;
> > > > + int set;
> > > > +
> > > > + now = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > > > + /* arbitrary 100 ms to do the commit */
> > > > + set = !!(now >= started + 100);
> > > > +
> > > > + if (offset == A_CXL_BI_RT_STATUS) {
> > > > + val = FIELD_DP32(val, CXL_BI_RT_STATUS, COMMITTED, set);
> > > > + } else {
> > > > + val = FIELD_DP32(val, CXL_BI_DECODER_STATUS, COMMITTED,
> > > > + set);
> > > > + }
> > > > + stl_le_p((uint8_t *)cache_mem + offset, val);
> > > > + }
> > > > + }
> > > > +
> > > > + return cregs->cache_mem_registers[offset / 4];
> > > > case 8:
> > > > qemu_log_mask(LOG_UNIMP,
> > > > "CXL 8 byte cache mem registers not implemented\n");
> > > > @@ -118,6 +148,47 @@ static void dumb_hdm_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > > > stl_le_p((uint8_t *)cache_mem + offset, value);
> > > > }
> > > >
> > > > +static void bi_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > > > + uint32_t value)
> > > > +{
> > > > + ComponentRegisters *cregs = &cxl_cstate->crb;
> > > > + uint32_t sts, *cache_mem = cregs->cache_mem_registers;
> > > > + bool to_commit = false;
> > > > + int type = 0; /* Unused value - work around for compiler warning */
> > > > +
> > > > + switch (offset) {
> > > > + case A_CXL_BI_RT_CTRL:
> > > > + to_commit = FIELD_EX32(value, CXL_BI_RT_CTRL, COMMIT);
> > > > + if (to_commit) {
> > > > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > > > + R_CXL_BI_RT_STATUS, 4);
> > > > + sts = FIELD_DP32(sts, CXL_BI_RT_STATUS, COMMITTED, 0);
> > > > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_RT_STATUS, sts);
> > > > + type = CXL_BISTATE_RT;
> > > > + }
> > > > + break;
> > > > + case A_CXL_BI_DECODER_CTRL:
> > > > + to_commit = FIELD_EX32(value, CXL_BI_DECODER_CTRL, COMMIT);
> > > > + if (to_commit) {
> > > > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > > > + R_CXL_BI_DECODER_STATUS, 4);
> > > > + sts = FIELD_DP32(sts, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > > > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_DECODER_STATUS, sts);
> > > > + type = CXL_BISTATE_DECODER;
> > > > + }
> > > > + break;
> > > > + default:
> > > > + break;
> > > > + }
> > > > +
> > > > + if (to_commit) {
> > > > + cxl_cstate->bi_state[type].last_commit =
> > > > + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > > > + }
> > > > +
> > > > + stl_le_p((uint8_t *)cache_mem + offset, value);
> > > > +}
> > > > +
> > > > static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > > > unsigned size)
> > > > {
> > > > @@ -141,6 +212,9 @@ static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > > > if (offset >= A_CXL_HDM_DECODER_CAPABILITY &&
> > > > offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) {
> > > > dumb_hdm_handler(cxl_cstate, offset, value);
> > > > + } else if (offset == A_CXL_BI_RT_CTRL ||
> > > > + offset == A_CXL_BI_DECODER_CTRL) {
> > > > + bi_handler(cxl_cstate, offset, value);
> > > > } else {
> > > > cregs->cache_mem_registers[offset / 4] = value;
> > > > }
> > > > @@ -230,7 +304,7 @@ static void ras_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > > > }
> > > >
> > > > static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > - enum reg_type type)
> > > > + enum reg_type type, bool bi)
> > > > {
> > > > int decoder_count = CXL_HDM_DECODER_COUNT;
> > > > int hdm_inc = R_CXL_HDM_DECODER1_BASE_LO - R_CXL_HDM_DECODER0_BASE_LO;
> > > > @@ -255,7 +329,9 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > UIO_DECODER_COUNT, 0);
> > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, MEMDATA_NXM_CAP, 0);
> > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY,
> > > > - SUPPORTED_COHERENCY_MODEL, 0); /* Unknown */
> > > > + SUPPORTED_COHERENCY_MODEL,
> > > > + /* host+dev or Unknown */
> > > > + type == CXL2_TYPE3_DEVICE && bi ? 3 : 0);
> > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_GLOBAL_CONTROL,
> > > > HDM_DECODER_ENABLE, 0);
> > > > write_msk[R_CXL_HDM_DECODER_GLOBAL_CONTROL] = 0x3;
> > > > @@ -278,9 +354,43 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > }
> > > > }
> > > >
> > > > +static void bi_rt_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > > > +{
> > > > + /* switch usp must commit the new BI-ID, timeout of 2secs */
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 1);
> > > > +
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CTRL, COMMIT, 0);
> > > > + write_msk[R_CXL_BI_RT_CTRL] = 0x1;
> > > > +
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMITTED, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 0x6);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 0x2);
> > > > +}
> > > > +
> > > > +static void bi_decoder_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > + enum reg_type type)
> > > > +{
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, HDM_D, 0);
> > > > + /* switch dsp must commit the new BI-ID, timeout of 2secs */
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT,
> > > > + (type != CXL2_ROOT_PORT && type != CXL2_TYPE3_DEVICE));
> > > > +
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_FW, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_ENABLE, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, COMMIT, 0);
> > > > + write_msk[R_CXL_BI_DECODER_CTRL] = 0x7;
> > > > +
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 0);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 0x6);
> > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 0x2);
> > > > +}
> > > > +
> > > > void cxl_component_register_init_common(uint32_t *reg_state,
> > > > uint32_t *write_msk,
> > > > - enum reg_type type)
> > > > + enum reg_type type,
> > > > + bool bi)
> > > > {
> > > > int caps = 0;
> > > >
> > > > @@ -320,7 +430,7 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > > > case CXL2_LOGICAL_DEVICE:
> > > > /* + HDM */
> > > > init_cap_reg(HDM, 5, 1);
> > > > - hdm_init_common(reg_state, write_msk, type);
> > > > + hdm_init_common(reg_state, write_msk, type, bi);
> > > > /* fallthrough */
> > > > case CXL2_DOWNSTREAM_PORT:
> > > > case CXL2_DEVICE:
> > > > @@ -335,6 +445,24 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > > > abort();
> > > > }
> > > >
> > > > + /* back invalidate */
> > > > + if (bi) {
> > > > + switch (type) {
> > > > + case CXL2_UPSTREAM_PORT:
> > > > + init_cap_reg(BI_RT, 11, CXL_BI_RT_CAP_VERSION);
> > > > + bi_rt_init_common(reg_state, write_msk);
> > > > + break;
> > > > + case CXL2_ROOT_PORT:
> > > > + case CXL2_DOWNSTREAM_PORT:
> > > > + case CXL2_TYPE3_DEVICE:
> > > > + init_cap_reg(BI_DECODER, 12, CXL_BI_DECODER_CAP_VERSION);
> > > > + bi_decoder_init_common(reg_state, write_msk, type);
> > > > + break;
> > > > + default:
> > > > + break;
> > > > + }
> > > > + }
> > > > +
> > > > ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, ARRAY_SIZE, caps);
> > > > #undef init_cap_reg
> > > > }
> > > > diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
> > > > index 3c7ecd8c48bc..3f09c589ae58 100644
> > > > --- a/hw/mem/cxl_type3.c
> > > > +++ b/hw/mem/cxl_type3.c
> > > > @@ -748,6 +748,11 @@ static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
> > > > return false;
> > > > }
> > > >
> > > > + if (!ct3d->flitmode && ct3d->hdmdb) {
> > > > + error_setg(errp, "hdm-db requires operating in 256b flit");
> > > > + return false;
> > > > + }
> > > > +
> > > > if (ct3d->hostvmem) {
> > > > MemoryRegion *vmr;
> > > > char *v_name;
> > > > @@ -1317,7 +1322,8 @@ static void ct3d_reset(DeviceState *dev)
> > > >
> > > > pcie_cap_fill_link_ep_usp(PCI_DEVICE(dev), ct3d->width, ct3d->speed,
> > > > ct3d->flitmode);
> > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_TYPE3_DEVICE);
> > > > + cxl_component_register_init_common(reg_state, write_msk,
> > > > + CXL2_TYPE3_DEVICE, ct3d->hdmdb);
> > > > cxl_device_register_init_t3(ct3d, CXL_T3_MSIX_MBOX);
> > > >
> > > > /*
> > > > @@ -1356,6 +1362,7 @@ static const Property ct3_props[] = {
> > > > DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLType3Dev,
> > > > width, PCIE_LINK_WIDTH_16),
> > > > DEFINE_PROP_BOOL("x-256b-flit", CXLType3Dev, flitmode, false),
> > > > + DEFINE_PROP_BOOL("hdm-db", CXLType3Dev, hdmdb, false),
> > > > };
> > > >
> > > > static uint64_t get_lsa_size(CXLType3Dev *ct3d)
> > > > diff --git a/hw/pci-bridge/cxl_downstream.c b/hw/pci-bridge/cxl_downstream.c
> > > > index 64086d8ec2f2..320818a8f1ce 100644
> > > > --- a/hw/pci-bridge/cxl_downstream.c
> > > > +++ b/hw/pci-bridge/cxl_downstream.c
> > > > @@ -39,7 +39,7 @@ static void latch_registers(CXLDownstreamPort *dsp)
> > > > uint32_t *write_msk = dsp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > >
> > > > cxl_component_register_init_common(reg_state, write_msk,
> > > > - CXL2_DOWNSTREAM_PORT);
> > > > + CXL2_DOWNSTREAM_PORT, true);
> > > > }
> > > >
> > > > /* TODO: Look at sharing this code across all CXL port types */
> > > > diff --git a/hw/pci-bridge/cxl_root_port.c b/hw/pci-bridge/cxl_root_port.c
> > > > index 5641048084a4..e2093ac39ee6 100644
> > > > --- a/hw/pci-bridge/cxl_root_port.c
> > > > +++ b/hw/pci-bridge/cxl_root_port.c
> > > > @@ -101,7 +101,8 @@ static void latch_registers(CXLRootPort *crp)
> > > > uint32_t *reg_state = crp->cxl_cstate.crb.cache_mem_registers;
> > > > uint32_t *write_msk = crp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > >
> > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT);
> > > > + cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT,
> > > > + true);
> > > > }
> > > >
> > > > static void build_dvsecs(PCIDevice *d, CXLComponentState *cxl)
> > > > diff --git a/hw/pci-bridge/cxl_upstream.c b/hw/pci-bridge/cxl_upstream.c
> > > > index c352d11dc7b7..fb8d19539c9f 100644
> > > > --- a/hw/pci-bridge/cxl_upstream.c
> > > > +++ b/hw/pci-bridge/cxl_upstream.c
> > > > @@ -90,7 +90,7 @@ static void latch_registers(CXLUpstreamPort *usp)
> > > > uint32_t *write_msk = usp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > >
> > > > cxl_component_register_init_common(reg_state, write_msk,
> > > > - CXL2_UPSTREAM_PORT);
> > > > + CXL2_UPSTREAM_PORT, usp->flitmode);
> > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, TARGET_COUNT, 8);
> > > > }
> > > >
> > > > diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
> > > > index b6e2eb796951..11623a5666f6 100644
> > > > --- a/hw/pci-bridge/pci_expander_bridge.c
> > > > +++ b/hw/pci-bridge/pci_expander_bridge.c
> > > > @@ -300,7 +300,7 @@ static void pxb_cxl_dev_reset(DeviceState *dev)
> > > > uint32_t *write_msk = cxl_cstate->crb.cache_mem_regs_write_mask;
> > > > int dsp_count = 0;
> > > >
> > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_RC);
> > > > + cxl_component_register_init_common(reg_state, write_msk, CXL2_RC, false);
> > > > /*
> > > > * The CXL specification allows for host bridges with no HDM decoders
> > > > * if they only have a single root port.
> > > > --
> > > > 2.51.0
> >
> >
>
>
On Wed, 4 Feb 2026 15:40:36 +0000
Jonathan Cameron <jonathan.cameron@huawei.com> wrote:
> On Wed, 4 Feb 2026 15:21:02 +0000
> Jonathan Cameron via qemu development <qemu-devel@nongnu.org> wrote:
>
> > On Wed, 4 Feb 2026 08:44:42 -0500
> > "Michael S. Tsirkin" <mst@redhat.com> wrote:
> >
> > > On Wed, Feb 04, 2026 at 08:24:55AM -0500, Michael S. Tsirkin wrote:
> > > > On Wed, Feb 04, 2026 at 12:12:14PM +0000, Jonathan Cameron wrote:
> > > > > From: Davidlohr Bueso <dave@stgolabs.net>
> > > > >
> > > > > Add basic plumbing for memory expander devices that support Back
> > > > > Invalidation. This introduces a 'hdm-db=on|off' parameter and
> > > > > exposes the relevant BI RT/Decoder component cachemem registers.
> > > > >
> > > > > Some noteworthy properties:
> > > > > - Devices require enabling Flit mode across the CXL topology.
> > > > > - Explicit BI-ID commit is required.
> > > > > - HDM decoder support both host and dev coherency models.
> > > > >
> > > > > Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
> > > > > Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> > > > > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > > >
> > > > more troubles:
> > > > https://gitlab.com/mstredhat/qemu/-/jobs/12984846000
> > >
> > >
> > > clang just as unhappy:
> > >
> > > https://gitlab.com/mstredhat/qemu/-/jobs/12984846060
> > They both seem to be clang.
> >
> > Replicated.
> >
> > Ah. This old gotcha - at one point I got one of my compiler colleagues to report
> > it as a clang bug but he lost the argument vs the spec. Though I believe
> > it is being fixed in the C spec longer term. I can't find the thread
> > now but we did discuss adding local scope in the macro a while back.
Did some archaeology
https://lore.kernel.org/qemu-devel/20231019124819.00005f6a@Huawei.com/
Can't add scope inside the macro as it's sometimes called outside
of functions. So it's a case of paper over this whenever we happen to hit
it.
Jonathan
> >
> > Anyhow work around is to add scope to avoid label for the case statement
> > being followed by _Static_assert()
> > Despite smelling like a function, it's not and has special rules...
> >
> > Would you like a v7 or squash the following in?
>
> Or. The problem only actually occurs after the next patch (which happens
> to bring the _static assert to the top of the case statement.)
> So drop patch 7 and I'll revisit just that little one at a later date.
>
> > Thanks
> >
> > Jonathan
> >
> >
> > diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> > index a3077184e230..07aabe331c44 100644
> > --- a/hw/cxl/cxl-component-utils.c
> > +++ b/hw/cxl/cxl-component-utils.c
> > @@ -68,7 +68,7 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> > ComponentRegisters *cregs = &cxl_cstate->crb;
> >
> > switch (size) {
> > - case 4:
> > + case 4: {
> > QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> >
> > if (offset == A_CXL_BI_RT_STATUS ||
> > @@ -101,6 +101,7 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> > }
> >
> > return cregs->cache_mem_registers[offset / 4];
> > + }
> > case 8:
> > qemu_log_mask(LOG_UNIMP,
> > "CXL 8 byte cache mem registers not implemented\n");
> >
> >
> > >
> > > >
> > > > > ---
> > > > > v6: Initialize type variable to avoid a false compiler warning
> > > > > from some versions of gcc. (Michael Tsirkin)
> > > > > ---
> > > > > docs/system/devices/cxl.rst | 23 +++++
> > > > > include/hw/cxl/cxl_component.h | 54 ++++++++++-
> > > > > include/hw/cxl/cxl_device.h | 3 +
> > > > > hw/cxl/cxl-component-utils.c | 142 ++++++++++++++++++++++++++--
> > > > > hw/mem/cxl_type3.c | 9 +-
> > > > > hw/pci-bridge/cxl_downstream.c | 2 +-
> > > > > hw/pci-bridge/cxl_root_port.c | 3 +-
> > > > > hw/pci-bridge/cxl_upstream.c | 2 +-
> > > > > hw/pci-bridge/pci_expander_bridge.c | 2 +-
> > > > > 9 files changed, 225 insertions(+), 15 deletions(-)
> > > > >
> > > > > diff --git a/docs/system/devices/cxl.rst b/docs/system/devices/cxl.rst
> > > > > index ca15a0da1c1d..9d0771cdfd73 100644
> > > > > --- a/docs/system/devices/cxl.rst
> > > > > +++ b/docs/system/devices/cxl.rst
> > > > > @@ -384,6 +384,29 @@ An example of 4 devices below a switch suitable for 1, 2 or 4 way interleave::
> > > > > -device cxl-type3,bus=swport3,persistent-memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem3,sn=0x4 \
> > > > > -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > > > >
> > > > > +An example of 4 type3 devices with volatile memory below a switch. Two of the devices
> > > > > +use HDM-DB for coherence, which requires operating in Flit mode::
> > > > > +
> > > > > + qemu-system-x86_64 -M q35,cxl=on -m 4G,maxmem=8G,slots=8 -smp 4 \
> > > > > + ...
> > > > > + -object memory-backend-ram,id=cxl-mem0,share=on,size=256M \
> > > > > + -object memory-backend-ram,id=cxl-mem1,share=on,size=256M \
> > > > > + -object memory-backend-ram,id=cxl-mem2,share=on,size=256M \
> > > > > + -object memory-backend-ram,id=cxl-mem3,share=on,size=256M \
> > > > > + -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
> > > > > + -device cxl-rp,port=0,bus=cxl.1,id=root_port0,chassis=0,slot=0 \
> > > > > + -device cxl-rp,port=1,bus=cxl.1,id=root_port1,chassis=0,slot=1 \
> > > > > + -device cxl-upstream,bus=root_port0,id=us0,x-256b-flit=on \
> > > > > + -device cxl-downstream,port=0,bus=us0,id=swport0,chassis=0,slot=4 \
> > > > > + -device cxl-type3,bus=swport0,volatile-memdev=cxl-mem0,id=cxl-mem0,sn=0x1,x-256b-flit=on,hdm-db=on \
> > > > > + -device cxl-downstream,port=1,bus=us0,id=swport1,chassis=0,slot=5 \
> > > > > + -device cxl-type3,bus=swport1,volatile-memdev=cxl-mem1,id=cxl-mem1,sn=0x2,x-256b-flit=on,hdm-db=on \
> > > > > + -device cxl-downstream,port=2,bus=us0,id=swport2,chassis=0,slot=6 \
> > > > > + -device cxl-type3,bus=swport2,volatile-memdev=cxl-mem2,id=cxl-mem2,sn=0x3 \
> > > > > + -device cxl-downstream,port=3,bus=us0,id=swport3,chassis=0,slot=7 \
> > > > > + -device cxl-type3,bus=swport3,volatile-memdev=cxl-mem3,id=cxl-mem3,sn=0x4 \
> > > > > + -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
> > > > > +
> > > > > A simple arm/virt example featuring a single direct connected CXL Type 3
> > > > > Volatile Memory device::
> > > > >
> > > > > diff --git a/include/hw/cxl/cxl_component.h b/include/hw/cxl/cxl_component.h
> > > > > index 1f167d3ef79b..ffc82202206c 100644
> > > > > --- a/include/hw/cxl/cxl_component.h
> > > > > +++ b/include/hw/cxl/cxl_component.h
> > > > > @@ -67,6 +67,8 @@ CXLx_CAPABILITY_HEADER(LINK, 2)
> > > > > CXLx_CAPABILITY_HEADER(HDM, 3)
> > > > > CXLx_CAPABILITY_HEADER(EXTSEC, 4)
> > > > > CXLx_CAPABILITY_HEADER(SNOOP, 5)
> > > > > +CXLx_CAPABILITY_HEADER(BI_RT, 6)
> > > > > +CXLx_CAPABILITY_HEADER(BI_DECODER, 7)
> > > > >
> > > > > /*
> > > > > * Capability structures contain the actual registers that the CXL component
> > > > > @@ -211,10 +213,55 @@ HDM_DECODER_INIT(3);
> > > > > (CXL_IDE_REGISTERS_OFFSET + CXL_IDE_REGISTERS_SIZE)
> > > > > #define CXL_SNOOP_REGISTERS_SIZE 0x8
> > > > >
> > > > > -QEMU_BUILD_BUG_MSG((CXL_SNOOP_REGISTERS_OFFSET +
> > > > > - CXL_SNOOP_REGISTERS_SIZE) >= 0x1000,
> > > > > +#define CXL_BI_RT_CAP_VERSION 1
> > > > > +#define CXL_BI_RT_REGISTERS_OFFSET \
> > > > > + (CXL_SNOOP_REGISTERS_OFFSET + CXL_SNOOP_REGISTERS_SIZE)
> > > > > +#define CXL_BI_RT_REGISTERS_SIZE 0xC
> > > > > +
> > > > > +REG32(CXL_BI_RT_CAPABILITY, CXL_BI_RT_REGISTERS_OFFSET)
> > > > > + FIELD(CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 0, 1)
> > > > > +REG32(CXL_BI_RT_CTRL, CXL_BI_RT_REGISTERS_OFFSET + 0x4)
> > > > > + FIELD(CXL_BI_RT_CTRL, COMMIT, 0, 1)
> > > > > +REG32(CXL_BI_RT_STATUS, CXL_BI_RT_REGISTERS_OFFSET + 0x8)
> > > > > + FIELD(CXL_BI_RT_STATUS, COMMITTED, 0, 1)
> > > > > + FIELD(CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > > > > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > > > > + FIELD(CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 12, 4)
> > > > > +
> > > > > +/* CXL r3.2 8.2.4.27 - CXL BI Decoder Capability Structure */
> > > > > +#define CXL_BI_DECODER_CAP_VERSION 1
> > > > > +#define CXL_BI_DECODER_REGISTERS_OFFSET \
> > > > > + (CXL_BI_RT_REGISTERS_OFFSET + CXL_BI_RT_REGISTERS_SIZE)
> > > > > +#define CXL_BI_DECODER_REGISTERS_SIZE 0xC
> > > > > +
> > > > > +REG32(CXL_BI_DECODER_CAPABILITY, CXL_BI_DECODER_REGISTERS_OFFSET)
> > > > > + FIELD(CXL_BI_DECODER_CAPABILITY, HDM_D, 0, 1)
> > > > > + FIELD(CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT, 1, 1)
> > > > > +REG32(CXL_BI_DECODER_CTRL, CXL_BI_DECODER_REGISTERS_OFFSET + 0x4)
> > > > > + FIELD(CXL_BI_DECODER_CTRL, BI_FW, 0, 1)
> > > > > + FIELD(CXL_BI_DECODER_CTRL, BI_ENABLE, 1, 1)
> > > > > + FIELD(CXL_BI_DECODER_CTRL, COMMIT, 2, 1)
> > > > > +REG32(CXL_BI_DECODER_STATUS, CXL_BI_DECODER_REGISTERS_OFFSET + 0x8)
> > > > > + FIELD(CXL_BI_DECODER_STATUS, COMMITTED, 0, 1)
> > > > > + FIELD(CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 1, 1)
> > > > > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 8, 4)
> > > > > + FIELD(CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 12, 4)
> > > > > +
> > > > > +QEMU_BUILD_BUG_MSG((CXL_BI_DECODER_REGISTERS_OFFSET +
> > > > > + CXL_BI_DECODER_REGISTERS_SIZE) >= 0x1000,
> > > > > "No space for registers");
> > > > >
> > > > > +/* track BI explicit commit handling for route table and decoder */
> > > > > +enum {
> > > > > + CXL_BISTATE_RT = 0,
> > > > > + CXL_BISTATE_DECODER,
> > > > > + CXL_BISTATE_MAX
> > > > > +};
> > > > > +
> > > > > +typedef struct bi_state {
> > > > > + uint64_t last_commit; /* last 0->1 transition */
> > > > > +} BIState;
> > > > > +
> > > > > typedef struct component_registers {
> > > > > /*
> > > > > * Main memory region to be registered with QEMU core.
> > > > > @@ -259,6 +306,7 @@ typedef struct cxl_component {
> > > > > };
> > > > >
> > > > > CDATObject cdat;
> > > > > + BIState bi_state[CXL_BISTATE_MAX];
> > > > > } CXLComponentState;
> > > > >
> > > > > void cxl_component_register_block_init(Object *obj,
> > > > > @@ -266,7 +314,7 @@ void cxl_component_register_block_init(Object *obj,
> > > > > const char *type);
> > > > > void cxl_component_register_init_common(uint32_t *reg_state,
> > > > > uint32_t *write_msk,
> > > > > - enum reg_type type);
> > > > > + enum reg_type type, bool bi);
> > > > >
> > > > > void cxl_component_create_dvsec(CXLComponentState *cxl_cstate,
> > > > > enum reg_type cxl_dev_type, uint16_t length,
> > > > > diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
> > > > > index 7d9236db8c85..393f3122173b 100644
> > > > > --- a/include/hw/cxl/cxl_device.h
> > > > > +++ b/include/hw/cxl/cxl_device.h
> > > > > @@ -770,6 +770,9 @@ struct CXLType3Dev {
> > > > > CXLMemSparingReadAttrs rank_sparing_attrs;
> > > > > CXLMemSparingWriteAttrs rank_sparing_wr_attrs;
> > > > >
> > > > > + /* BI flows */
> > > > > + bool hdmdb;
> > > > > +
> > > > > struct dynamic_capacity {
> > > > > HostMemoryBackend *host_dc;
> > > > > AddressSpace host_dc_as;
> > > > > diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> > > > > index 91770f103a85..a7d36e1128c2 100644
> > > > > --- a/hw/cxl/cxl-component-utils.c
> > > > > +++ b/hw/cxl/cxl-component-utils.c
> > > > > @@ -71,10 +71,40 @@ static uint64_t cxl_cache_mem_read_reg(void *opaque, hwaddr offset,
> > > > > case 4:
> > > > > if (cregs->special_ops && cregs->special_ops->read) {
> > > > > return cregs->special_ops->read(cxl_cstate, offset, 4);
> > > > > - } else {
> > > > > - QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > > > > - return cregs->cache_mem_registers[offset / 4];
> > > > > }
> > > > > +
> > > > > + QEMU_BUILD_BUG_ON(sizeof(*cregs->cache_mem_registers) != 4);
> > > > > +
> > > > > + if (offset == A_CXL_BI_RT_STATUS ||
> > > > > + offset == A_CXL_BI_DECODER_STATUS) {
> > > > > + int type;
> > > > > + uint64_t started;
> > > > > +
> > > > > + type = (offset == A_CXL_BI_RT_STATUS) ?
> > > > > + CXL_BISTATE_RT : CXL_BISTATE_DECODER;
> > > > > + started = cxl_cstate->bi_state[type].last_commit;
> > > > > +
> > > > > + if (started) {
> > > > > + uint32_t *cache_mem = cregs->cache_mem_registers;
> > > > > + uint32_t val = cache_mem[offset / 4];
> > > > > + uint64_t now;
> > > > > + int set;
> > > > > +
> > > > > + now = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > > > > + /* arbitrary 100 ms to do the commit */
> > > > > + set = !!(now >= started + 100);
> > > > > +
> > > > > + if (offset == A_CXL_BI_RT_STATUS) {
> > > > > + val = FIELD_DP32(val, CXL_BI_RT_STATUS, COMMITTED, set);
> > > > > + } else {
> > > > > + val = FIELD_DP32(val, CXL_BI_DECODER_STATUS, COMMITTED,
> > > > > + set);
> > > > > + }
> > > > > + stl_le_p((uint8_t *)cache_mem + offset, val);
> > > > > + }
> > > > > + }
> > > > > +
> > > > > + return cregs->cache_mem_registers[offset / 4];
> > > > > case 8:
> > > > > qemu_log_mask(LOG_UNIMP,
> > > > > "CXL 8 byte cache mem registers not implemented\n");
> > > > > @@ -118,6 +148,47 @@ static void dumb_hdm_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > > > > stl_le_p((uint8_t *)cache_mem + offset, value);
> > > > > }
> > > > >
> > > > > +static void bi_handler(CXLComponentState *cxl_cstate, hwaddr offset,
> > > > > + uint32_t value)
> > > > > +{
> > > > > + ComponentRegisters *cregs = &cxl_cstate->crb;
> > > > > + uint32_t sts, *cache_mem = cregs->cache_mem_registers;
> > > > > + bool to_commit = false;
> > > > > + int type = 0; /* Unused value - work around for compiler warning */
> > > > > +
> > > > > + switch (offset) {
> > > > > + case A_CXL_BI_RT_CTRL:
> > > > > + to_commit = FIELD_EX32(value, CXL_BI_RT_CTRL, COMMIT);
> > > > > + if (to_commit) {
> > > > > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > > > > + R_CXL_BI_RT_STATUS, 4);
> > > > > + sts = FIELD_DP32(sts, CXL_BI_RT_STATUS, COMMITTED, 0);
> > > > > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_RT_STATUS, sts);
> > > > > + type = CXL_BISTATE_RT;
> > > > > + }
> > > > > + break;
> > > > > + case A_CXL_BI_DECODER_CTRL:
> > > > > + to_commit = FIELD_EX32(value, CXL_BI_DECODER_CTRL, COMMIT);
> > > > > + if (to_commit) {
> > > > > + sts = cxl_cache_mem_read_reg(cxl_cstate,
> > > > > + R_CXL_BI_DECODER_STATUS, 4);
> > > > > + sts = FIELD_DP32(sts, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > > > > + stl_le_p((uint8_t *)cache_mem + R_CXL_BI_DECODER_STATUS, sts);
> > > > > + type = CXL_BISTATE_DECODER;
> > > > > + }
> > > > > + break;
> > > > > + default:
> > > > > + break;
> > > > > + }
> > > > > +
> > > > > + if (to_commit) {
> > > > > + cxl_cstate->bi_state[type].last_commit =
> > > > > + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
> > > > > + }
> > > > > +
> > > > > + stl_le_p((uint8_t *)cache_mem + offset, value);
> > > > > +}
> > > > > +
> > > > > static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > > > > unsigned size)
> > > > > {
> > > > > @@ -141,6 +212,9 @@ static void cxl_cache_mem_write_reg(void *opaque, hwaddr offset, uint64_t value,
> > > > > if (offset >= A_CXL_HDM_DECODER_CAPABILITY &&
> > > > > offset <= A_CXL_HDM_DECODER3_TARGET_LIST_HI) {
> > > > > dumb_hdm_handler(cxl_cstate, offset, value);
> > > > > + } else if (offset == A_CXL_BI_RT_CTRL ||
> > > > > + offset == A_CXL_BI_DECODER_CTRL) {
> > > > > + bi_handler(cxl_cstate, offset, value);
> > > > > } else {
> > > > > cregs->cache_mem_registers[offset / 4] = value;
> > > > > }
> > > > > @@ -230,7 +304,7 @@ static void ras_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > > > > }
> > > > >
> > > > > static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > > - enum reg_type type)
> > > > > + enum reg_type type, bool bi)
> > > > > {
> > > > > int decoder_count = CXL_HDM_DECODER_COUNT;
> > > > > int hdm_inc = R_CXL_HDM_DECODER1_BASE_LO - R_CXL_HDM_DECODER0_BASE_LO;
> > > > > @@ -255,7 +329,9 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > > UIO_DECODER_COUNT, 0);
> > > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, MEMDATA_NXM_CAP, 0);
> > > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY,
> > > > > - SUPPORTED_COHERENCY_MODEL, 0); /* Unknown */
> > > > > + SUPPORTED_COHERENCY_MODEL,
> > > > > + /* host+dev or Unknown */
> > > > > + type == CXL2_TYPE3_DEVICE && bi ? 3 : 0);
> > > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_GLOBAL_CONTROL,
> > > > > HDM_DECODER_ENABLE, 0);
> > > > > write_msk[R_CXL_HDM_DECODER_GLOBAL_CONTROL] = 0x3;
> > > > > @@ -278,9 +354,43 @@ static void hdm_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > > }
> > > > > }
> > > > >
> > > > > +static void bi_rt_init_common(uint32_t *reg_state, uint32_t *write_msk)
> > > > > +{
> > > > > + /* switch usp must commit the new BI-ID, timeout of 2secs */
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CAPABILITY, EXPLICIT_COMMIT, 1);
> > > > > +
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_CTRL, COMMIT, 0);
> > > > > + write_msk[R_CXL_BI_RT_CTRL] = 0x1;
> > > > > +
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMITTED, 0);
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, ERR_NOT_COMMITTED, 0);
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_SCALE, 0x6);
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_RT_STATUS, COMMIT_TMO_BASE, 0x2);
> > > > > +}
> > > > > +
> > > > > +static void bi_decoder_init_common(uint32_t *reg_state, uint32_t *write_msk,
> > > > > + enum reg_type type)
> > > > > +{
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, HDM_D, 0);
> > > > > + /* switch dsp must commit the new BI-ID, timeout of 2secs */
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CAPABILITY, EXPLICIT_COMMIT,
> > > > > + (type != CXL2_ROOT_PORT && type != CXL2_TYPE3_DEVICE));
> > > > > +
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_FW, 0);
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, BI_ENABLE, 0);
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_CTRL, COMMIT, 0);
> > > > > + write_msk[R_CXL_BI_DECODER_CTRL] = 0x7;
> > > > > +
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMITTED, 0);
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, ERR_NOT_COMMITTED, 0);
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_SCALE, 0x6);
> > > > > + ARRAY_FIELD_DP32(reg_state, CXL_BI_DECODER_STATUS, COMMIT_TMO_BASE, 0x2);
> > > > > +}
> > > > > +
> > > > > void cxl_component_register_init_common(uint32_t *reg_state,
> > > > > uint32_t *write_msk,
> > > > > - enum reg_type type)
> > > > > + enum reg_type type,
> > > > > + bool bi)
> > > > > {
> > > > > int caps = 0;
> > > > >
> > > > > @@ -320,7 +430,7 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > > > > case CXL2_LOGICAL_DEVICE:
> > > > > /* + HDM */
> > > > > init_cap_reg(HDM, 5, 1);
> > > > > - hdm_init_common(reg_state, write_msk, type);
> > > > > + hdm_init_common(reg_state, write_msk, type, bi);
> > > > > /* fallthrough */
> > > > > case CXL2_DOWNSTREAM_PORT:
> > > > > case CXL2_DEVICE:
> > > > > @@ -335,6 +445,24 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> > > > > abort();
> > > > > }
> > > > >
> > > > > + /* back invalidate */
> > > > > + if (bi) {
> > > > > + switch (type) {
> > > > > + case CXL2_UPSTREAM_PORT:
> > > > > + init_cap_reg(BI_RT, 11, CXL_BI_RT_CAP_VERSION);
> > > > > + bi_rt_init_common(reg_state, write_msk);
> > > > > + break;
> > > > > + case CXL2_ROOT_PORT:
> > > > > + case CXL2_DOWNSTREAM_PORT:
> > > > > + case CXL2_TYPE3_DEVICE:
> > > > > + init_cap_reg(BI_DECODER, 12, CXL_BI_DECODER_CAP_VERSION);
> > > > > + bi_decoder_init_common(reg_state, write_msk, type);
> > > > > + break;
> > > > > + default:
> > > > > + break;
> > > > > + }
> > > > > + }
> > > > > +
> > > > > ARRAY_FIELD_DP32(reg_state, CXL_CAPABILITY_HEADER, ARRAY_SIZE, caps);
> > > > > #undef init_cap_reg
> > > > > }
> > > > > diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
> > > > > index 3c7ecd8c48bc..3f09c589ae58 100644
> > > > > --- a/hw/mem/cxl_type3.c
> > > > > +++ b/hw/mem/cxl_type3.c
> > > > > @@ -748,6 +748,11 @@ static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
> > > > > return false;
> > > > > }
> > > > >
> > > > > + if (!ct3d->flitmode && ct3d->hdmdb) {
> > > > > + error_setg(errp, "hdm-db requires operating in 256b flit");
> > > > > + return false;
> > > > > + }
> > > > > +
> > > > > if (ct3d->hostvmem) {
> > > > > MemoryRegion *vmr;
> > > > > char *v_name;
> > > > > @@ -1317,7 +1322,8 @@ static void ct3d_reset(DeviceState *dev)
> > > > >
> > > > > pcie_cap_fill_link_ep_usp(PCI_DEVICE(dev), ct3d->width, ct3d->speed,
> > > > > ct3d->flitmode);
> > > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_TYPE3_DEVICE);
> > > > > + cxl_component_register_init_common(reg_state, write_msk,
> > > > > + CXL2_TYPE3_DEVICE, ct3d->hdmdb);
> > > > > cxl_device_register_init_t3(ct3d, CXL_T3_MSIX_MBOX);
> > > > >
> > > > > /*
> > > > > @@ -1356,6 +1362,7 @@ static const Property ct3_props[] = {
> > > > > DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLType3Dev,
> > > > > width, PCIE_LINK_WIDTH_16),
> > > > > DEFINE_PROP_BOOL("x-256b-flit", CXLType3Dev, flitmode, false),
> > > > > + DEFINE_PROP_BOOL("hdm-db", CXLType3Dev, hdmdb, false),
> > > > > };
> > > > >
> > > > > static uint64_t get_lsa_size(CXLType3Dev *ct3d)
> > > > > diff --git a/hw/pci-bridge/cxl_downstream.c b/hw/pci-bridge/cxl_downstream.c
> > > > > index 64086d8ec2f2..320818a8f1ce 100644
> > > > > --- a/hw/pci-bridge/cxl_downstream.c
> > > > > +++ b/hw/pci-bridge/cxl_downstream.c
> > > > > @@ -39,7 +39,7 @@ static void latch_registers(CXLDownstreamPort *dsp)
> > > > > uint32_t *write_msk = dsp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > > >
> > > > > cxl_component_register_init_common(reg_state, write_msk,
> > > > > - CXL2_DOWNSTREAM_PORT);
> > > > > + CXL2_DOWNSTREAM_PORT, true);
> > > > > }
> > > > >
> > > > > /* TODO: Look at sharing this code across all CXL port types */
> > > > > diff --git a/hw/pci-bridge/cxl_root_port.c b/hw/pci-bridge/cxl_root_port.c
> > > > > index 5641048084a4..e2093ac39ee6 100644
> > > > > --- a/hw/pci-bridge/cxl_root_port.c
> > > > > +++ b/hw/pci-bridge/cxl_root_port.c
> > > > > @@ -101,7 +101,8 @@ static void latch_registers(CXLRootPort *crp)
> > > > > uint32_t *reg_state = crp->cxl_cstate.crb.cache_mem_registers;
> > > > > uint32_t *write_msk = crp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > > >
> > > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT);
> > > > > + cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT,
> > > > > + true);
> > > > > }
> > > > >
> > > > > static void build_dvsecs(PCIDevice *d, CXLComponentState *cxl)
> > > > > diff --git a/hw/pci-bridge/cxl_upstream.c b/hw/pci-bridge/cxl_upstream.c
> > > > > index c352d11dc7b7..fb8d19539c9f 100644
> > > > > --- a/hw/pci-bridge/cxl_upstream.c
> > > > > +++ b/hw/pci-bridge/cxl_upstream.c
> > > > > @@ -90,7 +90,7 @@ static void latch_registers(CXLUpstreamPort *usp)
> > > > > uint32_t *write_msk = usp->cxl_cstate.crb.cache_mem_regs_write_mask;
> > > > >
> > > > > cxl_component_register_init_common(reg_state, write_msk,
> > > > > - CXL2_UPSTREAM_PORT);
> > > > > + CXL2_UPSTREAM_PORT, usp->flitmode);
> > > > > ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, TARGET_COUNT, 8);
> > > > > }
> > > > >
> > > > > diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
> > > > > index b6e2eb796951..11623a5666f6 100644
> > > > > --- a/hw/pci-bridge/pci_expander_bridge.c
> > > > > +++ b/hw/pci-bridge/pci_expander_bridge.c
> > > > > @@ -300,7 +300,7 @@ static void pxb_cxl_dev_reset(DeviceState *dev)
> > > > > uint32_t *write_msk = cxl_cstate->crb.cache_mem_regs_write_mask;
> > > > > int dsp_count = 0;
> > > > >
> > > > > - cxl_component_register_init_common(reg_state, write_msk, CXL2_RC);
> > > > > + cxl_component_register_init_common(reg_state, write_msk, CXL2_RC, false);
> > > > > /*
> > > > > * The CXL specification allows for host bridges with no HDM decoders
> > > > > * if they only have a single root port.
> > > > > --
> > > > > 2.51.0
> > >
> > >
> >
> >
>
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