From: Jonathan Cameron <jonathan.cameron@huawei.com>

These memops perform interleave decoding, walking down the
CXL topology from CFMWS described host interleave
decoder via CXL host bridge HDM decoders, through the CXL
root ports and finally call CXL type 3 specific read and write
functions.

Note that, whilst functional the current implementation does
not support:
* switches
* multiple HDM decoders at a given level.
* unaligned accesses across the interleave boundaries

Signed-off-by: Jonathan Cameron <jonathan.cameron@huawei.com>
---
 hw/cxl/cxl-host.c    | 125 +++++++++++++++++++++++++++++++++++++++++++
 include/hw/cxl/cxl.h |   2 +
 2 files changed, 127 insertions(+)

diff --git a/hw/cxl/cxl-host.c b/hw/cxl/cxl-host.c
index 9f303e6d8e..d9cad188a8 100644
--- a/hw/cxl/cxl-host.c
+++ b/hw/cxl/cxl-host.c
@@ -136,3 +136,128 @@ void cxl_fixed_memory_window_link_targets(Error **errp)
         }
     }
 }
+
+/* TODO: support, multiple hdm decoders */
+static bool cxl_hdm_find_target(uint32_t *cache_mem, hwaddr addr,
+                                uint8_t *target)
+{
+    uint32_t ctrl;
+    uint32_t ig_enc;
+    uint32_t iw_enc;
+    uint32_t target_reg;
+    uint32_t target_idx;
+
+    ctrl = cache_mem[R_CXL_HDM_DECODER0_CTRL];
+    if (!FIELD_EX32(ctrl, CXL_HDM_DECODER0_CTRL, COMMITTED)) {
+        return false;
+    }
+
+    ig_enc = FIELD_EX32(ctrl, CXL_HDM_DECODER0_CTRL, IG);
+    iw_enc = FIELD_EX32(ctrl, CXL_HDM_DECODER0_CTRL, IW);
+    target_idx = (addr / cxl_decode_ig(ig_enc)) % (1 << iw_enc);
+
+    if (target_idx > 4) {
+        target_reg = cache_mem[R_CXL_HDM_DECODER0_TARGET_LIST_LO];
+        target_reg >>= target_idx * 8;
+    } else {
+        target_reg = cache_mem[R_CXL_HDM_DECODER0_TARGET_LIST_LO];
+        target_reg >>= (target_idx - 4) * 8;
+    }
+    *target = target_reg & 0xff;
+
+    return true;
+}
+
+static PCIDevice *cxl_cfmws_find_device(CXLFixedWindow *fw, hwaddr addr)
+{
+    CXLComponentState *hb_cstate;
+    PCIHostState *hb;
+    int rb_index;
+    uint32_t *cache_mem;
+    uint8_t target;
+    bool target_found;
+    PCIDevice *rp, *d;
+
+    /* Address is relative to memory region. Convert to HPA */
+    addr += fw->base;
+
+    rb_index = (addr / cxl_decode_ig(fw->enc_int_gran)) % fw->num_targets;
+    hb = PCI_HOST_BRIDGE(fw->target_hbs[rb_index]->cxl.cxl_host_bridge);
+    if (!hb || !hb->bus || !pci_bus_is_cxl(hb->bus)) {
+        return NULL;
+    }
+
+    hb_cstate = cxl_get_hb_cstate(hb);
+    if (!hb_cstate) {
+        return NULL;
+    }
+
+    cache_mem = hb_cstate->crb.cache_mem_registers;
+
+    target_found = cxl_hdm_find_target(cache_mem, addr, &target);
+    if (!target_found) {
+        return NULL;
+    }
+
+    rp = pcie_find_port_by_pn(hb->bus, target);
+    if (!rp) {
+        return NULL;
+    }
+
+    d = pci_bridge_get_sec_bus(PCI_BRIDGE(rp))->devices[0];
+
+    if (!d || !object_dynamic_cast(OBJECT(d), TYPE_CXL_TYPE3_DEV)) {
+        return NULL;
+    }
+
+    return d;
+}
+
+static MemTxResult cxl_read_cfmws(void *opaque, hwaddr addr, uint64_t *data,
+                                  unsigned size, MemTxAttrs attrs)
+{
+    CXLFixedWindow *fw = opaque;
+    PCIDevice *d;
+
+    d = cxl_cfmws_find_device(fw, addr);
+    if (d == NULL) {
+        *data = 0;
+        /* Reads to invalid address return poison */
+        return MEMTX_ERROR;
+    }
+
+    return cxl_type3_read(d, addr + fw->base, data, size, attrs);
+}
+
+static MemTxResult cxl_write_cfmws(void *opaque, hwaddr addr,
+                                   uint64_t data, unsigned size,
+                                   MemTxAttrs attrs)
+{
+    CXLFixedWindow *fw = opaque;
+    PCIDevice *d;
+
+    d = cxl_cfmws_find_device(fw, addr);
+    if (d == NULL) {
+        /* Writes to invalid address are silent */
+        return MEMTX_OK;
+    }
+
+    return cxl_type3_write(d, addr + fw->base, data, size, attrs);
+}
+
+const MemoryRegionOps cfmws_ops = {
+    .read_with_attrs = cxl_read_cfmws,
+    .write_with_attrs = cxl_write_cfmws,
+    .endianness = DEVICE_LITTLE_ENDIAN,
+    .valid = {
+        .min_access_size = 1,
+        .max_access_size = 8,
+        .unaligned = true,
+    },
+    .impl = {
+        .min_access_size = 1,
+        .max_access_size = 8,
+        .unaligned = true,
+    },
+};
+
diff --git a/include/hw/cxl/cxl.h b/include/hw/cxl/cxl.h
index 1b72c0b7b7..260d602ec9 100644
--- a/include/hw/cxl/cxl.h
+++ b/include/hw/cxl/cxl.h
@@ -46,4 +46,6 @@ extern QemuOptsList qemu_cxl_fixed_window_opts;
 void parse_cxl_fixed_memory_window_opts(MachineState *ms);
 void cxl_fixed_memory_window_link_targets(Error **errp);
 
+extern const MemoryRegionOps cfmws_ops;
+
 #endif
-- 
2.32.0