From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>
One of advantages of using this protocol over ACPI-based PC DIMM hotplug is
that it allows hot-adding memory in much smaller granularity because the
ACPI DIMM slot limit does not apply.
In order to enable this functionality a new memory backend needs to be
created and provided to the driver via the "memdev" parameter.
This can be achieved by, for example, adding
"-object memory-backend-ram,id=mem1,size=32G" to the QEMU command line and
then instantiating the driver with "memdev=mem1" parameter.
The device will try to use multiple memslots to cover the memory backend in
order to reduce the size of metadata for the not-yet-hot-added part of the
memory backend.
Co-developed-by: David Hildenbrand <david@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
---
hw/hyperv/hv-balloon-our_range_memslots.c | 201 ++++++++
hw/hyperv/hv-balloon-our_range_memslots.h | 110 +++++
hw/hyperv/hv-balloon.c | 566 +++++++++++++++++++++-
hw/hyperv/meson.build | 2 +-
hw/hyperv/trace-events | 5 +
5 files changed, 878 insertions(+), 6 deletions(-)
create mode 100644 hw/hyperv/hv-balloon-our_range_memslots.c
create mode 100644 hw/hyperv/hv-balloon-our_range_memslots.h
diff --git a/hw/hyperv/hv-balloon-our_range_memslots.c b/hw/hyperv/hv-balloon-our_range_memslots.c
new file mode 100644
index 000000000000..99bae870f371
--- /dev/null
+++ b/hw/hyperv/hv-balloon-our_range_memslots.c
@@ -0,0 +1,201 @@
+/*
+ * QEMU Hyper-V Dynamic Memory Protocol driver
+ *
+ * Copyright (C) 2020-2023 Oracle and/or its affiliates.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "hv-balloon-internal.h"
+#include "hv-balloon-our_range_memslots.h"
+#include "trace.h"
+
+/* OurRange */
+static void our_range_init(OurRange *our_range, uint64_t start, uint64_t count)
+{
+ assert(count <= UINT64_MAX - start);
+ our_range->range.start = start;
+ our_range->range.count = count;
+
+ hvb_page_range_tree_init(&our_range->removed_guest);
+ hvb_page_range_tree_init(&our_range->removed_both);
+
+ /* mark the whole range as unused but for potential use */
+ our_range->added = 0;
+ our_range->unusable_tail = 0;
+}
+
+static void our_range_destroy(OurRange *our_range)
+{
+ hvb_page_range_tree_destroy(&our_range->removed_guest);
+ hvb_page_range_tree_destroy(&our_range->removed_both);
+}
+
+void hvb_our_range_clear_removed_trees(OurRange *our_range)
+{
+ hvb_page_range_tree_destroy(&our_range->removed_guest);
+ hvb_page_range_tree_destroy(&our_range->removed_both);
+ hvb_page_range_tree_init(&our_range->removed_guest);
+ hvb_page_range_tree_init(&our_range->removed_both);
+}
+
+void hvb_our_range_mark_added(OurRange *our_range, uint64_t additional_size)
+{
+ assert(additional_size <= UINT64_MAX - our_range->added);
+
+ our_range->added += additional_size;
+
+ assert(our_range->added <= UINT64_MAX - our_range->unusable_tail);
+ assert(our_range->added + our_range->unusable_tail <=
+ our_range->range.count);
+}
+
+/* OurRangeMemslots */
+static void our_range_memslots_init_slots(OurRangeMemslots *our_range,
+ MemoryRegion *backing_mr,
+ Object *memslot_owner)
+{
+ OurRangeMemslotsSlots *memslots = &our_range->slots;
+ unsigned int idx;
+ uint64_t memslot_offset;
+
+ assert(memslots->count > 0);
+ memslots->slots = g_new0(MemoryRegion, memslots->count);
+
+ /* Initialize our memslots, but don't map them yet. */
+ assert(memslots->size_each > 0);
+ for (idx = 0, memslot_offset = 0; idx < memslots->count;
+ idx++, memslot_offset += memslots->size_each) {
+ uint64_t memslot_size;
+ g_autofree char *name = NULL;
+
+ /* The size of the last memslot might be smaller. */
+ if (idx == memslots->count - 1) {
+ uint64_t region_size;
+
+ assert(our_range->mr);
+ region_size = memory_region_size(our_range->mr);
+ memslot_size = region_size - memslot_offset;
+ } else {
+ memslot_size = memslots->size_each;
+ }
+
+ name = g_strdup_printf("memslot-%u", idx);
+ memory_region_init_alias(&memslots->slots[idx], memslot_owner, name,
+ backing_mr, memslot_offset, memslot_size);
+ /*
+ * We want to be able to atomically and efficiently activate/deactivate
+ * individual memslots without affecting adjacent memslots in memory
+ * notifiers.
+ */
+ memory_region_set_unmergeable(&memslots->slots[idx], true);
+ }
+
+ memslots->mapped_count = 0;
+}
+
+OurRangeMemslots *hvb_our_range_memslots_new(uint64_t addr,
+ MemoryRegion *parent_mr,
+ MemoryRegion *backing_mr,
+ Object *memslot_owner,
+ unsigned int memslot_count,
+ uint64_t memslot_size)
+{
+ OurRangeMemslots *our_range;
+
+ our_range = g_malloc(sizeof(*our_range));
+ our_range_init(&our_range->range,
+ addr / HV_BALLOON_PAGE_SIZE,
+ memory_region_size(parent_mr) / HV_BALLOON_PAGE_SIZE);
+ our_range->slots.size_each = memslot_size;
+ our_range->slots.count = memslot_count;
+ our_range->mr = parent_mr;
+ our_range_memslots_init_slots(our_range, backing_mr, memslot_owner);
+
+ return our_range;
+}
+
+static void our_range_memslots_free_memslots(OurRangeMemslots *our_range)
+{
+ OurRangeMemslotsSlots *memslots = &our_range->slots;
+ unsigned int idx;
+ uint64_t offset;
+
+ memory_region_transaction_begin();
+ for (idx = 0, offset = 0; idx < memslots->mapped_count;
+ idx++, offset += memslots->size_each) {
+ trace_hv_balloon_unmap_slot(idx, memslots->count, offset);
+ assert(memory_region_is_mapped(&memslots->slots[idx]));
+ memory_region_del_subregion(our_range->mr, &memslots->slots[idx]);
+ }
+ memory_region_transaction_commit();
+
+ for (idx = 0; idx < memslots->count; idx++) {
+ object_unparent(OBJECT(&memslots->slots[idx]));
+ }
+
+ g_clear_pointer(&our_range->slots.slots, g_free);
+}
+
+void hvb_our_range_memslots_free(OurRangeMemslots *our_range)
+{
+ OurRangeMemslotsSlots *memslots = &our_range->slots;
+ MemoryRegion *hostmem_mr;
+ RAMBlock *rb;
+
+ assert(our_range->slots.count > 0);
+ assert(our_range->slots.slots);
+
+ hostmem_mr = memslots->slots[0].alias;
+ rb = hostmem_mr->ram_block;
+ ram_block_discard_range(rb, 0, qemu_ram_get_used_length(rb));
+
+ our_range_memslots_free_memslots(our_range);
+ our_range_destroy(&our_range->range);
+ g_free(our_range);
+}
+
+void hvb_our_range_memslots_ensure_mapped_additional(OurRangeMemslots *our_range,
+ uint64_t additional_map_size)
+{
+ OurRangeMemslotsSlots *memslots = &our_range->slots;
+ uint64_t total_map_size;
+ unsigned int idx;
+ uint64_t offset;
+
+ total_map_size = (our_range->range.added + additional_map_size) *
+ HV_BALLOON_PAGE_SIZE;
+ idx = memslots->mapped_count;
+ assert(memslots->size_each > 0);
+ offset = idx * memslots->size_each;
+
+ /*
+ * Activate all memslots covered by the newly added region in a single
+ * transaction.
+ */
+ memory_region_transaction_begin();
+ for ( ; idx < memslots->count;
+ idx++, offset += memslots->size_each) {
+ /*
+ * If this memslot starts beyond or at the end of the range to map so
+ * does every next one.
+ */
+ if (offset >= total_map_size) {
+ break;
+ }
+
+ /*
+ * Instead of enabling/disabling memslot, we add/remove them. This
+ * should make address space updates faster, because we don't have to
+ * loop over many disabled subregions.
+ */
+ trace_hv_balloon_map_slot(idx, memslots->count, offset);
+ assert(!memory_region_is_mapped(&memslots->slots[idx]));
+ memory_region_add_subregion(our_range->mr, offset,
+ &memslots->slots[idx]);
+
+ memslots->mapped_count++;
+ }
+ memory_region_transaction_commit();
+}
diff --git a/hw/hyperv/hv-balloon-our_range_memslots.h b/hw/hyperv/hv-balloon-our_range_memslots.h
new file mode 100644
index 000000000000..b6f592d34b09
--- /dev/null
+++ b/hw/hyperv/hv-balloon-our_range_memslots.h
@@ -0,0 +1,110 @@
+/*
+ * QEMU Hyper-V Dynamic Memory Protocol driver
+ *
+ * Copyright (C) 2020-2023 Oracle and/or its affiliates.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef HW_HYPERV_HV_BALLOON_OUR_RANGE_MEMSLOTS_H
+#define HW_HYPERV_HV_BALLOON_OUR_RANGE_MEMSLOTS_H
+
+#include "qemu/osdep.h"
+
+#include "exec/memory.h"
+#include "qom/object.h"
+#include "hv-balloon-page_range_tree.h"
+
+/* OurRange */
+#define OUR_RANGE(ptr) ((OurRange *)(ptr))
+
+/* "our range" means the memory range owned by this driver (for hot-adding) */
+typedef struct OurRange {
+ PageRange range;
+
+ /* How many pages were hot-added to the guest */
+ uint64_t added;
+
+ /* Pages at the end not currently usable */
+ uint64_t unusable_tail;
+
+ /* Memory removed from the guest */
+ PageRangeTree removed_guest, removed_both;
+} OurRange;
+
+static inline uint64_t our_range_get_remaining_start(OurRange *our_range)
+{
+ return our_range->range.start + our_range->added;
+}
+
+static inline uint64_t our_range_get_remaining_size(OurRange *our_range)
+{
+ return our_range->range.count - our_range->added - our_range->unusable_tail;
+}
+
+void hvb_our_range_mark_added(OurRange *our_range, uint64_t additional_size);
+
+static inline void our_range_mark_remaining_unusable(OurRange *our_range)
+{
+ our_range->unusable_tail = our_range->range.count - our_range->added;
+}
+
+static inline PageRangeTree our_range_get_removed_tree(OurRange *our_range,
+ bool both)
+{
+ if (both) {
+ return our_range->removed_both;
+ } else {
+ return our_range->removed_guest;
+ }
+}
+
+static inline bool our_range_is_removed_tree_empty(OurRange *our_range,
+ bool both)
+{
+ if (both) {
+ return page_range_tree_is_empty(our_range->removed_both);
+ } else {
+ return page_range_tree_is_empty(our_range->removed_guest);
+ }
+}
+
+void hvb_our_range_clear_removed_trees(OurRange *our_range);
+
+/* OurRangeMemslots */
+typedef struct OurRangeMemslotsSlots {
+ /* Nominal size of each memslot (the last one might be smaller) */
+ uint64_t size_each;
+
+ /* Slots array and its element count */
+ MemoryRegion *slots;
+ unsigned int count;
+
+ /* How many slots are currently mapped */
+ unsigned int mapped_count;
+} OurRangeMemslotsSlots;
+
+typedef struct OurRangeMemslots {
+ OurRange range;
+
+ /* Memslots covering our range */
+ OurRangeMemslotsSlots slots;
+
+ MemoryRegion *mr;
+} OurRangeMemslots;
+
+OurRangeMemslots *hvb_our_range_memslots_new(uint64_t addr,
+ MemoryRegion *parent_mr,
+ MemoryRegion *backing_mr,
+ Object *memslot_owner,
+ unsigned int memslot_count,
+ uint64_t memslot_size);
+void hvb_our_range_memslots_free(OurRangeMemslots *our_range);
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(OurRangeMemslots, hvb_our_range_memslots_free)
+
+void hvb_our_range_memslots_ensure_mapped_additional(OurRangeMemslots *our_range,
+ uint64_t additional_map_size);
+
+#endif
diff --git a/hw/hyperv/hv-balloon.c b/hw/hyperv/hv-balloon.c
index 5f3674ba0642..5999f1127d87 100644
--- a/hw/hyperv/hv-balloon.c
+++ b/hw/hyperv/hv-balloon.c
@@ -34,9 +34,12 @@
#include "sysemu/balloon.h"
#include "sysemu/hostmem.h"
#include "sysemu/reset.h"
+#include "hv-balloon-our_range_memslots.h"
#include "hv-balloon-page_range_tree.h"
#include "trace.h"
+#define HV_BALLOON_ADDR_PROP "addr"
+#define HV_BALLOON_MEMDEV_PROP "memdev"
#define HV_BALLOON_GUID "525074DC-8985-46e2-8057-A307DC18A502"
/*
@@ -52,6 +55,8 @@
#define HV_BALLOON_HA_CHUNK_SIZE (2 * GiB)
#define HV_BALLOON_HA_CHUNK_PAGES (HV_BALLOON_HA_CHUNK_SIZE / HV_BALLOON_PAGE_SIZE)
+#define HV_BALLOON_HA_MEMSLOT_SIZE_ALIGN (128 * MiB)
+
#define HV_BALLOON_HR_CHUNK_PAGES 585728
/*
* ^ that's the maximum number of pages
@@ -88,6 +93,10 @@ typedef enum State {
S_UNBALLOON_POSTING,
S_UNBALLOON_RB_WAIT,
S_UNBALLOON_REPLY_WAIT,
+ S_HOT_ADD_SETUP,
+ S_HOT_ADD_RB_WAIT,
+ S_HOT_ADD_POSTING,
+ S_HOT_ADD_REPLY_WAIT,
} State;
typedef struct StateDesc {
@@ -117,25 +126,43 @@ typedef struct HvBalloon {
uint64_t target;
bool target_changed;
- /* Current (un)balloon */
+ /* Current (un)balloon / hot-add operation parameters */
union {
uint64_t balloon_diff;
struct {
uint64_t unballoon_diff;
+ uint64_t hot_add_diff;
+ };
+
+ struct {
+ PageRange hot_add_range;
+ uint64_t ha_current_count;
};
};
+ OurRangeMemslots *our_range;
+
+ /* Count of memslots covering our memory */
+ unsigned int memslot_count;
+
/* Nominal size of each memslot (the last one might be smaller) */
uint64_t memslot_size;
+ /* Non-ours removed memory */
PageRangeTree removed_guest, removed_both;
+ /* Grand totals of removed memory (both ours and non-ours) */
uint64_t removed_guest_ctr, removed_both_ctr;
+
+ /* MEMORY_DEVICE props */
+ uint64_t addr;
+ HostMemoryBackend *hostmem;
+ MemoryRegion *mr;
} HvBalloon;
OBJECT_DEFINE_TYPE_WITH_INTERFACES(HvBalloon, hv_balloon, HV_BALLOON, VMBUS_DEVICE, \
- { })
+ { TYPE_MEMORY_DEVICE }, { })
#define HV_BALLOON_SET_STATE(hvb, news) \
do { \
@@ -155,6 +182,16 @@ typedef struct HvBalloonReq {
VMBusChanReq vmreq;
} HvBalloonReq;
+/* total our memory includes parts currently removed from the guest */
+static uint64_t hv_balloon_total_our_ram(HvBalloon *balloon)
+{
+ if (!balloon->our_range) {
+ return 0;
+ }
+
+ return balloon->our_range->range.added;
+}
+
/* TODO: unify the code below with virtio-balloon and cache the value */
static int build_dimm_list(Object *obj, void *opaque)
{
@@ -193,10 +230,11 @@ static uint64_t hv_balloon_total_ram(HvBalloon *balloon)
{
ram_addr_t ram_size = get_current_ram_size();
uint64_t ram_size_pages = ram_size >> HV_BALLOON_PFN_SHIFT;
+ uint64_t our_ram_size_pages = hv_balloon_total_our_ram(balloon);
assert(ram_size_pages > 0);
- return ram_size_pages;
+ return SUM_SATURATE_U64(ram_size_pages, our_ram_size_pages);
}
/*
@@ -275,14 +313,30 @@ static ssize_t hv_balloon_send_packet(VMBusChannel *chan,
static bool hv_balloon_unballoon_get_source(HvBalloon *balloon,
PageRangeTree *dtree,
- uint64_t **dctr)
+ uint64_t **dctr,
+ bool *is_our_range)
{
+ OurRange *our_range = OUR_RANGE(balloon->our_range);
+
+ /* Try the boot memory first */
if (g_tree_nnodes(balloon->removed_guest.t) > 0) {
*dtree = balloon->removed_guest;
*dctr = &balloon->removed_guest_ctr;
+ *is_our_range = false;
} else if (g_tree_nnodes(balloon->removed_both.t) > 0) {
*dtree = balloon->removed_both;
*dctr = &balloon->removed_both_ctr;
+ *is_our_range = false;
+ } else if (!our_range) {
+ return false;
+ } else if (!our_range_is_removed_tree_empty(our_range, false)) {
+ *dtree = our_range_get_removed_tree(our_range, false);
+ *dctr = &balloon->removed_guest_ctr;
+ *is_our_range = true;
+ } else if (!our_range_is_removed_tree_empty(our_range, true)) {
+ *dtree = our_range_get_removed_tree(our_range, true);
+ *dctr = &balloon->removed_both_ctr;
+ *is_our_range = true;
} else {
return false;
}
@@ -310,6 +364,7 @@ static void hv_balloon_unballoon_posting(HvBalloon *balloon, StateDesc *stdesc)
VMBusChannel *chan = hv_balloon_get_channel(balloon);
PageRangeTree dtree;
uint64_t *dctr;
+ bool our_range;
struct dm_unballoon_request *ur;
size_t ur_size = sizeof(*ur) + sizeof(ur->range_array[0]);
PageRange range;
@@ -319,7 +374,7 @@ static void hv_balloon_unballoon_posting(HvBalloon *balloon, StateDesc *stdesc)
assert(balloon->state == S_UNBALLOON_POSTING);
assert(balloon->unballoon_diff > 0);
- if (!hv_balloon_unballoon_get_source(balloon, &dtree, &dctr)) {
+ if (!hv_balloon_unballoon_get_source(balloon, &dtree, &dctr, &our_range)) {
error_report("trying to unballoon but nothing seems to be ballooned");
/*
* there is little we can do as we might have already
@@ -328,6 +383,7 @@ static void hv_balloon_unballoon_posting(HvBalloon *balloon, StateDesc *stdesc)
return;
}
+ assert(balloon->our_range || !our_range);
assert(dtree.t);
assert(dctr);
@@ -369,6 +425,166 @@ static void hv_balloon_unballoon_posting(HvBalloon *balloon, StateDesc *stdesc)
}
}
+static bool hv_balloon_our_range_ensure(HvBalloon *balloon)
+{
+ uint64_t align;
+ MemoryRegion *hostmem_mr;
+ g_autoptr(OurRangeMemslots) our_range_memslots = NULL;
+ OurRange *our_range;
+
+ if (balloon->our_range) {
+ return true;
+ }
+
+ if (!balloon->hostmem) {
+ return false;
+ }
+
+ align = (1 << balloon->caps.cap_bits.hot_add_alignment) * MiB;
+ assert(QEMU_IS_ALIGNED(balloon->addr, align));
+
+ hostmem_mr = host_memory_backend_get_memory(balloon->hostmem);
+
+ our_range_memslots = hvb_our_range_memslots_new(balloon->addr,
+ balloon->mr, hostmem_mr,
+ OBJECT(balloon),
+ balloon->memslot_count,
+ balloon->memslot_size);
+ our_range = OUR_RANGE(our_range_memslots);
+
+ if (hvb_page_range_tree_intree_any(balloon->removed_guest,
+ our_range->range.start,
+ our_range->range.count) ||
+ hvb_page_range_tree_intree_any(balloon->removed_both,
+ our_range->range.start,
+ our_range->range.count)) {
+ error_report("some parts of the memory backend were already returned by the guest. this should not happen, please reboot the guest and try again");
+ return false;
+ }
+
+ trace_hv_balloon_our_range_add(our_range->range.count,
+ our_range->range.start);
+
+ balloon->our_range = g_steal_pointer(&our_range_memslots);
+ return true;
+}
+
+static void hv_balloon_hot_add_setup(HvBalloon *balloon, StateDesc *stdesc)
+{
+ /* need to make copy since it is in union with hot_add_range */
+ uint64_t hot_add_diff = balloon->hot_add_diff;
+ PageRange *hot_add_range = &balloon->hot_add_range;
+ uint64_t align, our_range_remaining;
+ OurRange *our_range;
+
+ assert(balloon->state == S_HOT_ADD_SETUP);
+ assert(hot_add_diff > 0);
+
+ if (!hv_balloon_our_range_ensure(balloon)) {
+ goto ret_idle;
+ }
+
+ our_range = OUR_RANGE(balloon->our_range);
+
+ align = (1 << balloon->caps.cap_bits.hot_add_alignment) *
+ (MiB / HV_BALLOON_PAGE_SIZE);
+
+ /* Absolute GPA in pages */
+ hot_add_range->start = our_range_get_remaining_start(our_range);
+ assert(QEMU_IS_ALIGNED(hot_add_range->start, align));
+
+ our_range_remaining = our_range_get_remaining_size(our_range);
+ hot_add_range->count = MIN(our_range_remaining, hot_add_diff);
+ hot_add_range->count = QEMU_ALIGN_DOWN(hot_add_range->count, align);
+ if (hot_add_range->count == 0) {
+ goto ret_idle;
+ }
+
+ hvb_our_range_memslots_ensure_mapped_additional(balloon->our_range,
+ hot_add_range->count);
+
+ HV_BALLOON_STATE_DESC_SET(stdesc, S_HOT_ADD_RB_WAIT);
+ return;
+
+ret_idle:
+ HV_BALLOON_STATE_DESC_SET(stdesc, S_IDLE);
+}
+
+static void hv_balloon_hot_add_rb_wait(HvBalloon *balloon, StateDesc *stdesc)
+{
+ VMBusChannel *chan = hv_balloon_get_channel(balloon);
+ struct dm_hot_add *ha;
+ size_t ha_size = sizeof(*ha) + sizeof(ha->range);
+
+ assert(balloon->state == S_HOT_ADD_RB_WAIT);
+
+ if (vmbus_channel_reserve(chan, 0, ha_size) < 0) {
+ return;
+ }
+
+ HV_BALLOON_STATE_DESC_SET(stdesc, S_HOT_ADD_POSTING);
+}
+
+static void hv_balloon_hot_add_posting(HvBalloon *balloon, StateDesc *stdesc)
+{
+ PageRange *hot_add_range = &balloon->hot_add_range;
+ uint64_t *current_count = &balloon->ha_current_count;
+ VMBusChannel *chan = hv_balloon_get_channel(balloon);
+ struct dm_hot_add *ha;
+ size_t ha_size = sizeof(*ha) + sizeof(ha->range);
+ union dm_mem_page_range *ha_region;
+ uint64_t align, chunk_max_size;
+ ssize_t ret;
+
+ assert(balloon->state == S_HOT_ADD_POSTING);
+ assert(hot_add_range->count > 0);
+
+ align = (1 << balloon->caps.cap_bits.hot_add_alignment) *
+ (MiB / HV_BALLOON_PAGE_SIZE);
+ if (align >= HV_BALLOON_HA_CHUNK_PAGES) {
+ /*
+ * If the required alignment is higher than the chunk size we let it
+ * override that size.
+ */
+ chunk_max_size = align;
+ } else {
+ chunk_max_size = QEMU_ALIGN_DOWN(HV_BALLOON_HA_CHUNK_PAGES, align);
+ }
+
+ /*
+ * hot_add_range->count starts aligned in hv_balloon_hot_add_setup(),
+ * then it is either reduced by subtracting aligned current_count or
+ * further hot-adds are prevented by marking the whole remaining our range
+ * as unusable in hv_balloon_handle_hot_add_response().
+ */
+ *current_count = MIN(hot_add_range->count, chunk_max_size);
+
+ ha = alloca(ha_size);
+ ha_region = &(&ha->range)[1];
+ memset(ha, 0, ha_size);
+ ha->hdr.type = DM_MEM_HOT_ADD_REQUEST;
+ ha->hdr.size = ha_size;
+ ha->hdr.trans_id = balloon->trans_id;
+
+ ha->range.finfo.start_page = hot_add_range->start;
+ ha->range.finfo.page_cnt = *current_count;
+ ha_region->finfo.start_page = hot_add_range->start;
+ ha_region->finfo.page_cnt = ha->range.finfo.page_cnt;
+
+ trace_hv_balloon_outgoing_hot_add(ha->hdr.trans_id,
+ *current_count, hot_add_range->start);
+
+ ret = vmbus_channel_send(chan, VMBUS_PACKET_DATA_INBAND,
+ NULL, 0, ha, ha_size, false,
+ ha->hdr.trans_id);
+ if (ret <= 0) {
+ error_report("error %zd when posting hot add msg, expect problems",
+ ret);
+ }
+
+ HV_BALLOON_STATE_DESC_SET(stdesc, S_HOT_ADD_REPLY_WAIT);
+}
+
static void hv_balloon_balloon_rb_wait(HvBalloon *balloon, StateDesc *stdesc)
{
VMBusChannel *chan = hv_balloon_get_channel(balloon);
@@ -428,14 +644,23 @@ static void hv_balloon_idle_state_process_target(HvBalloon *balloon,
* the procedure is in progress
*/
if (balloon->target > ram_size_pages - total_removed) {
+ bool can_hot_add = balloon->caps.cap_bits.hot_add;
uint64_t target_diff = balloon->target -
(ram_size_pages - total_removed);
balloon->unballoon_diff = MIN(target_diff, total_removed);
+ if (can_hot_add) {
+ balloon->hot_add_diff = target_diff - balloon->unballoon_diff;
+ } else {
+ balloon->hot_add_diff = 0;
+ }
+
if (balloon->unballoon_diff > 0) {
assert(can_balloon);
HV_BALLOON_STATE_DESC_SET(stdesc, S_UNBALLOON_RB_WAIT);
+ } else if (balloon->hot_add_diff > 0) {
+ HV_BALLOON_STATE_DESC_SET(stdesc, S_HOT_ADD_SETUP);
}
} else if (can_balloon &&
balloon->target < ram_size_pages - total_removed) {
@@ -465,6 +690,9 @@ static const struct {
[S_BALLOON_RB_WAIT].handler = hv_balloon_balloon_rb_wait,
[S_UNBALLOON_POSTING].handler = hv_balloon_unballoon_posting,
[S_UNBALLOON_RB_WAIT].handler = hv_balloon_unballoon_rb_wait,
+ [S_HOT_ADD_SETUP].handler = hv_balloon_hot_add_setup,
+ [S_HOT_ADD_RB_WAIT].handler = hv_balloon_hot_add_rb_wait,
+ [S_HOT_ADD_POSTING].handler = hv_balloon_hot_add_posting,
};
static void hv_balloon_handle_state(HvBalloon *balloon, StateDesc *stdesc)
@@ -507,13 +735,64 @@ static void hv_balloon_remove_response_handle_range(HvBalloon *balloon,
bool both,
uint64_t *removedctr)
{
+ OurRange *our_range = OUR_RANGE(balloon->our_range);
PageRangeTree globaltree =
both ? balloon->removed_both : balloon->removed_guest;
uint64_t *globalctr =
both ? &balloon->removed_both_ctr : &balloon->removed_guest_ctr;
+ PageRange rangeeff;
+
+ if (range->count == 0) {
+ return;
+ }
trace_hv_balloon_remove_response(range->count, range->start, both);
+ if (our_range) {
+ /* Includes the not-yet-hot-added and unusable parts. */
+ rangeeff = our_range->range;
+ } else {
+ rangeeff.start = rangeeff.count = 0;
+ }
+
+ if (page_range_intersection_size(range, rangeeff.start, rangeeff.count) > 0) {
+ PageRangeTree ourtree = our_range_get_removed_tree(our_range, both);
+ PageRange rangehole, rangecommon;
+ uint64_t ourremoved = 0;
+
+ /* process the hole before our range, if it exists */
+ page_range_part_before(range, rangeeff.start, &rangehole);
+ hv_balloon_remove_response_insert_range(globaltree, &rangehole,
+ globalctr, removedctr, NULL);
+ if (rangehole.count > 0) {
+ trace_hv_balloon_remove_response_hole(rangehole.count,
+ rangehole.start,
+ range->count, range->start,
+ rangeeff.start, both);
+ }
+
+ /* process our part */
+ page_range_intersect(range, rangeeff.start, rangeeff.count,
+ &rangecommon);
+ hv_balloon_remove_response_insert_range(ourtree, &rangecommon,
+ globalctr, removedctr,
+ &ourremoved);
+ if (rangecommon.count > 0) {
+ trace_hv_balloon_remove_response_common(rangecommon.count,
+ rangecommon.start,
+ range->count, range->start,
+ rangeeff.count,
+ rangeeff.start, ourremoved,
+ both);
+ }
+
+ /* calculate what's left after our range */
+ rangecommon = *range;
+ page_range_part_after(&rangecommon, rangeeff.start, rangeeff.count,
+ range);
+ }
+
+ /* process the remainder of the range that lies after our range */
if (range->count > 0) {
hv_balloon_remove_response_insert_range(globaltree, range,
globalctr, removedctr, NULL);
@@ -847,6 +1126,72 @@ static void hv_balloon_handle_unballoon_response(HvBalloon *balloon,
balloon->trans_id++;
+ if (balloon->hot_add_diff > 0) {
+ bool can_hot_add = balloon->caps.cap_bits.hot_add;
+
+ assert(can_hot_add);
+ HV_BALLOON_STATE_DESC_SET(stdesc, S_HOT_ADD_SETUP);
+ } else {
+ HV_BALLOON_STATE_DESC_SET(stdesc, S_IDLE);
+ }
+}
+
+static void hv_balloon_handle_hot_add_response(HvBalloon *balloon,
+ HvBalloonReq *req,
+ StateDesc *stdesc)
+{
+ PageRange *hot_add_range = &balloon->hot_add_range;
+ VMBusChanReq *vmreq = &req->vmreq;
+ struct dm_hot_add_response *msgHaR = vmreq->msg;
+ OurRange *our_range;
+
+ if (balloon->state != S_HOT_ADD_REPLY_WAIT) {
+ warn_report("unexpected DM_HOT_ADD_RESPONSE in %d state",
+ balloon->state);
+ return;
+ }
+
+ assert(balloon->our_range);
+ our_range = OUR_RANGE(balloon->our_range);
+
+ if (!hv_balloon_handle_msg_size(req, sizeof(*msgHaR),
+ "DM_HOT_ADD_RESPONSE"))
+ return;
+
+ trace_hv_balloon_incoming_hot_add(msgHaR->hdr.trans_id, msgHaR->result,
+ msgHaR->page_count);
+
+ balloon->trans_id++;
+
+ if (msgHaR->result) {
+ if (msgHaR->page_count > balloon->ha_current_count) {
+ warn_report("DM_HOT_ADD_RESPONSE page count higher than requested (%"PRIu32" vs %"PRIu64")",
+ msgHaR->page_count, balloon->ha_current_count);
+ msgHaR->page_count = balloon->ha_current_count;
+ }
+
+ hvb_our_range_mark_added(our_range, msgHaR->page_count);
+ hot_add_range->start += msgHaR->page_count;
+ hot_add_range->count -= msgHaR->page_count;
+ }
+
+ if (!msgHaR->result || msgHaR->page_count < balloon->ha_current_count) {
+ /*
+ * the current planned range was only partially hot-added, take note
+ * how much of it remains and don't attempt any further hot adds
+ */
+ our_range_mark_remaining_unusable(our_range);
+
+ goto ret_idle;
+ }
+
+ /* any pages remaining to hot-add in our range? */
+ if (hot_add_range->count > 0) {
+ HV_BALLOON_STATE_DESC_SET(stdesc, S_HOT_ADD_RB_WAIT);
+ return;
+ }
+
+ret_idle:
HV_BALLOON_STATE_DESC_SET(stdesc, S_IDLE);
}
@@ -924,6 +1269,10 @@ static void hv_balloon_handle_packet(HvBalloon *balloon, HvBalloonReq *req,
hv_balloon_handle_status_report(balloon, req);
break;
+ case DM_MEM_HOT_ADD_RESPONSE:
+ hv_balloon_handle_hot_add_response(balloon, req, stdesc);
+ break;
+
case DM_UNBALLOON_RESPONSE:
hv_balloon_handle_unballoon_response(balloon, req, stdesc);
break;
@@ -1072,6 +1421,61 @@ static void hv_balloon_post_init_timer(void *opaque)
hv_balloon_event_loop(balloon);
}
+static void hv_balloon_system_reset_unrealize_common(HvBalloon *balloon)
+{
+ g_clear_pointer(&balloon->our_range, hvb_our_range_memslots_free);
+}
+
+static void hv_balloon_system_reset(void *opaque)
+{
+ HvBalloon *balloon = HV_BALLOON(opaque);
+
+ hv_balloon_system_reset_unrealize_common(balloon);
+}
+
+static void hv_balloon_ensure_mr(HvBalloon *balloon)
+{
+ MemoryRegion *hostmem_mr;
+
+ assert(balloon->hostmem);
+
+ if (balloon->mr) {
+ return;
+ }
+
+ hostmem_mr = host_memory_backend_get_memory(balloon->hostmem);
+
+ balloon->mr = g_new0(MemoryRegion, 1);
+ memory_region_init(balloon->mr, OBJECT(balloon), TYPE_HV_BALLOON,
+ memory_region_size(hostmem_mr));
+
+ /*
+ * The VM can indicate an alignment up to 32 GiB. Memory device core can
+ * usually only handle/guarantee 1 GiB alignment. The user will have to
+ * specify a larger maxmem eventually.
+ *
+ * The memory device core will warn the user in case maxmem might have to be
+ * increased and will fail plugging the device if there is not sufficient
+ * space after alignment.
+ *
+ * TODO: we could do the alignment ourselves in a slightly bigger region.
+ * But this feels better, although the warning might be annoying. Maybe
+ * we can optimize that in the future (e.g., with such a device on the
+ * cmdline place/size the device memory region differently.
+ */
+ balloon->mr->align = MAX(32 * GiB, memory_region_get_alignment(hostmem_mr));
+}
+
+static void hv_balloon_free_mr(HvBalloon *balloon)
+{
+ if (!balloon->mr) {
+ return;
+ }
+
+ object_unparent(OBJECT(balloon->mr));
+ g_clear_pointer(&balloon->mr, g_free);
+}
+
static void hv_balloon_vmdev_realize(VMBusDevice *vdev, Error **errp)
{
ERRP_GUARD();
@@ -1088,13 +1492,52 @@ static void hv_balloon_vmdev_realize(VMBusDevice *vdev, Error **errp)
return;
}
+ if (balloon->hostmem) {
+ if (host_memory_backend_is_mapped(balloon->hostmem)) {
+ Object *obj = OBJECT(balloon->hostmem);
+
+ error_setg(errp, "'%s' property specifies a busy memdev: %s",
+ HV_BALLOON_MEMDEV_PROP,
+ object_get_canonical_path_component(obj));
+ goto out_balloon_handler;
+ }
+
+ hv_balloon_ensure_mr(balloon);
+
+ /* This is rather unlikely to happen, but let's still check for it. */
+ if (!QEMU_IS_ALIGNED(memory_region_size(balloon->mr),
+ HV_BALLOON_PAGE_SIZE)) {
+ error_setg(errp, "'%s' property memdev size has to be a multiple of 0x%" PRIx64,
+ HV_BALLOON_MEMDEV_PROP, (uint64_t)HV_BALLOON_PAGE_SIZE);
+ goto out_balloon_handler;
+ }
+
+ host_memory_backend_set_mapped(balloon->hostmem, true);
+ vmstate_register_ram(host_memory_backend_get_memory(balloon->hostmem),
+ DEVICE(balloon));
+ } else if (balloon->addr) {
+ error_setg(errp, "'%s' property must not be set without a memdev",
+ HV_BALLOON_MEMDEV_PROP);
+ goto out_balloon_handler;
+ }
+
timer_init_ms(&balloon->post_init_timer, QEMU_CLOCK_VIRTUAL,
hv_balloon_post_init_timer, balloon);
+
+ qemu_register_reset(hv_balloon_system_reset, balloon);
+
+ return;
+
+out_balloon_handler:
+ qemu_remove_balloon_handler(balloon);
}
/*
* VMBus device reset has to be implemented in case the guest decides to
* disconnect and reconnect to the VMBus without rebooting the whole system.
+ *
+ * However, the hot-added memory can't be removed here as Windows keeps on using
+ * it until the system is restarted, even after disconnecting from the VMBus.
*/
static void hv_balloon_vmdev_reset(VMBusDevice *vdev)
{
@@ -1104,6 +1547,10 @@ static void hv_balloon_vmdev_reset(VMBusDevice *vdev)
return;
}
+ if (balloon->our_range) {
+ hvb_our_range_clear_removed_trees(OUR_RANGE(balloon->our_range));
+ }
+
hvb_page_range_tree_destroy(&balloon->removed_guest);
hvb_page_range_tree_destroy(&balloon->removed_both);
hvb_page_range_tree_init(&balloon->removed_guest);
@@ -1117,14 +1564,106 @@ static void hv_balloon_vmdev_reset(VMBusDevice *vdev)
hv_balloon_event_loop(balloon);
}
+/*
+ * Clean up things that were (possibly) allocated pre-realization, for example
+ * from memory_device_pre_plug(), so we don't leak them if the device don't
+ * actually get realized in the end.
+ */
+static void hv_balloon_unrealize_finalize_common(HvBalloon *balloon)
+{
+ hv_balloon_free_mr(balloon);
+ balloon->addr = 0;
+
+ balloon->memslot_count = 0;
+}
+
static void hv_balloon_vmdev_unrealize(VMBusDevice *vdev)
{
HvBalloon *balloon = HV_BALLOON(vdev);
+ qemu_unregister_reset(hv_balloon_system_reset, balloon);
+
+ hv_balloon_system_reset_unrealize_common(balloon);
+
qemu_remove_balloon_handler(balloon);
+ if (balloon->hostmem) {
+ vmstate_unregister_ram(host_memory_backend_get_memory(balloon->hostmem),
+ DEVICE(balloon));
+ host_memory_backend_set_mapped(balloon->hostmem, false);
+ }
+
hvb_page_range_tree_destroy(&balloon->removed_guest);
hvb_page_range_tree_destroy(&balloon->removed_both);
+
+ hv_balloon_unrealize_finalize_common(balloon);
+}
+
+static uint64_t hv_balloon_md_get_addr(const MemoryDeviceState *md)
+{
+ return object_property_get_uint(OBJECT(md), HV_BALLOON_ADDR_PROP,
+ &error_abort);
+}
+
+static void hv_balloon_md_set_addr(MemoryDeviceState *md, uint64_t addr,
+ Error **errp)
+{
+ object_property_set_uint(OBJECT(md), HV_BALLOON_ADDR_PROP, addr, errp);
+}
+
+static MemoryRegion *hv_balloon_md_get_memory_region(MemoryDeviceState *md,
+ Error **errp)
+{
+ HvBalloon *balloon = HV_BALLOON(md);
+
+ if (!balloon->hostmem) {
+ return NULL;
+ }
+
+ hv_balloon_ensure_mr(balloon);
+
+ return balloon->mr;
+}
+
+static void hv_balloon_decide_memslots(MemoryDeviceState *md,
+ unsigned int limit)
+{
+ HvBalloon *balloon = HV_BALLOON(md);
+ MemoryRegion *hostmem_mr;
+ uint64_t region_size, memslot_size, memslots;
+
+ /* We're called exactly once, before realizing the device. */
+ assert(!balloon->memslot_count);
+
+ /* We should not be called if we don't have a memory backend */
+ assert(balloon->hostmem);
+
+ hostmem_mr = host_memory_backend_get_memory(balloon->hostmem);
+ region_size = memory_region_size(hostmem_mr);
+
+ assert(region_size > 0);
+ memslot_size = QEMU_ALIGN_UP(region_size / limit,
+ HV_BALLOON_HA_MEMSLOT_SIZE_ALIGN);
+ memslots = QEMU_ALIGN_UP(region_size, memslot_size) / memslot_size;
+
+ if (memslots > 1) {
+ balloon->memslot_size = memslot_size;
+ } else {
+ balloon->memslot_size = region_size;
+ }
+
+ assert(memslots <= UINT_MAX);
+ balloon->memslot_count = memslots;
+}
+
+static unsigned int hv_balloon_get_memslots(MemoryDeviceState *md)
+{
+ const HvBalloon *balloon = HV_BALLOON(md);
+
+ /* We're called after setting the suggested limit. */
+ assert(balloon->memslot_count > 0);
+
+ return balloon->memslot_count;
}
static void hv_balloon_init(Object *obj)
@@ -1133,12 +1672,20 @@ static void hv_balloon_init(Object *obj)
static void hv_balloon_finalize(Object *obj)
{
+ HvBalloon *balloon = HV_BALLOON(obj);
+
+ hv_balloon_unrealize_finalize_common(balloon);
}
static Property hv_balloon_properties[] = {
DEFINE_PROP_BOOL("status-report", HvBalloon,
status_report.enabled, false),
+ /* MEMORY_DEVICE props */
+ DEFINE_PROP_LINK(HV_BALLOON_MEMDEV_PROP, HvBalloon, hostmem,
+ TYPE_MEMORY_BACKEND, HostMemoryBackend *),
+ DEFINE_PROP_UINT64(HV_BALLOON_ADDR_PROP, HvBalloon, addr, 0),
+
DEFINE_PROP_END_OF_LIST(),
};
@@ -1146,6 +1693,7 @@ static void hv_balloon_class_init(ObjectClass *klass, void *data)
{
DeviceClass *dc = DEVICE_CLASS(klass);
VMBusDeviceClass *vdc = VMBUS_DEVICE_CLASS(klass);
+ MemoryDeviceClass *mdc = MEMORY_DEVICE_CLASS(klass);
device_class_set_props(dc, hv_balloon_properties);
qemu_uuid_parse(HV_BALLOON_GUID, &vdc->classid);
@@ -1157,4 +1705,12 @@ static void hv_balloon_class_init(ObjectClass *klass, void *data)
vdc->open_channel = hv_balloon_vmdev_open_channel;
vdc->close_channel = hv_balloon_vmdev_close_channel;
vdc->chan_notify_cb = hv_balloon_vmdev_chan_notify;
+
+ mdc->get_addr = hv_balloon_md_get_addr;
+ mdc->set_addr = hv_balloon_md_set_addr;
+ mdc->get_plugged_size = memory_device_get_region_size;
+ mdc->get_memory_region = hv_balloon_md_get_memory_region;
+ mdc->decide_memslots = hv_balloon_decide_memslots;
+ mdc->get_memslots = hv_balloon_get_memslots;
+ /* implement fill_device_info */
}
diff --git a/hw/hyperv/meson.build b/hw/hyperv/meson.build
index b5be1cbb1a96..852d4f4a2ee2 100644
--- a/hw/hyperv/meson.build
+++ b/hw/hyperv/meson.build
@@ -2,4 +2,4 @@ specific_ss.add(when: 'CONFIG_HYPERV', if_true: files('hyperv.c'))
specific_ss.add(when: 'CONFIG_HYPERV_TESTDEV', if_true: files('hyperv_testdev.c'))
specific_ss.add(when: 'CONFIG_VMBUS', if_true: files('vmbus.c'))
specific_ss.add(when: 'CONFIG_SYNDBG', if_true: files('syndbg.c'))
-specific_ss.add(when: 'CONFIG_HV_BALLOON', if_true: files('hv-balloon.c', 'hv-balloon-page_range_tree.c'))
+specific_ss.add(when: 'CONFIG_HV_BALLOON', if_true: files('hv-balloon.c', 'hv-balloon-page_range_tree.c', 'hv-balloon-our_range_memslots.c'))
diff --git a/hw/hyperv/trace-events b/hw/hyperv/trace-events
index 86c724ba661b..7963c215b1c5 100644
--- a/hw/hyperv/trace-events
+++ b/hw/hyperv/trace-events
@@ -23,9 +23,14 @@ hv_balloon_incoming_version(uint16_t major, uint16_t minor) "incoming proto vers
hv_balloon_incoming_caps(uint32_t caps) "incoming caps 0x%x"
hv_balloon_outgoing_unballoon(uint32_t trans_id, uint64_t count, uint64_t start, uint64_t rempages) "posting unballoon %"PRIu32" for %"PRIu64" @ 0x%"PRIx64", remaining %"PRIu64
hv_balloon_incoming_unballoon(uint32_t trans_id) "incoming unballoon response %"PRIu32
+hv_balloon_outgoing_hot_add(uint32_t trans_id, uint64_t count, uint64_t start) "posting hot add %"PRIu32" for %"PRIu64" @ 0x%"PRIx64
+hv_balloon_incoming_hot_add(uint32_t trans_id, uint32_t result, uint32_t count) "incoming hot add response %"PRIu32", result %"PRIu32", count %"PRIu32
hv_balloon_outgoing_balloon(uint32_t trans_id, uint64_t count, uint64_t rempages) "posting balloon %"PRIu32" for %"PRIu64", remaining %"PRIu64
hv_balloon_incoming_balloon(uint32_t trans_id, uint32_t range_count, uint32_t more_pages) "incoming balloon response %"PRIu32", ranges %"PRIu32", more %"PRIu32
+hv_balloon_our_range_add(uint64_t count, uint64_t start) "adding our range %"PRIu64" @ 0x%"PRIx64
hv_balloon_remove_response(uint64_t count, uint64_t start, unsigned int both) "processing remove response range %"PRIu64" @ 0x%"PRIx64", both %u"
hv_balloon_remove_response_hole(uint64_t counthole, uint64_t starthole, uint64_t countrange, uint64_t startrange, uint64_t starthpr, unsigned int both) "response range hole %"PRIu64" @ 0x%"PRIx64" from range %"PRIu64" @ 0x%"PRIx64", before our start 0x%"PRIx64", both %u"
hv_balloon_remove_response_common(uint64_t countcommon, uint64_t startcommon, uint64_t countrange, uint64_t startrange, uint64_t counthpr, uint64_t starthpr, uint64_t removed, unsigned int both) "response common range %"PRIu64" @ 0x%"PRIx64" from range %"PRIu64" @ 0x%"PRIx64" with our %"PRIu64" @ 0x%"PRIx64", removed %"PRIu64", both %u"
hv_balloon_remove_response_remainder(uint64_t count, uint64_t start, unsigned int both) "remove response remaining range %"PRIu64" @ 0x%"PRIx64", both %u"
+hv_balloon_map_slot(unsigned int idx, unsigned int total_slots, uint64_t offset) "mapping memslot %u / %u @ 0x%"PRIx64
+hv_balloon_unmap_slot(unsigned int idx, unsigned int total_slots, uint64_t offset) "unmapping memslot %u / %u @ 0x%"PRIx64On Mon, 6 Nov 2023 at 14:23, Maciej S. Szmigiero
<mail@maciej.szmigiero.name> wrote:
>
> From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>
>
> One of advantages of using this protocol over ACPI-based PC DIMM hotplug is
> that it allows hot-adding memory in much smaller granularity because the
> ACPI DIMM slot limit does not apply.
>
> In order to enable this functionality a new memory backend needs to be
> created and provided to the driver via the "memdev" parameter.
>
> This can be achieved by, for example, adding
> "-object memory-backend-ram,id=mem1,size=32G" to the QEMU command line and
> then instantiating the driver with "memdev=mem1" parameter.
>
> The device will try to use multiple memslots to cover the memory backend in
> order to reduce the size of metadata for the not-yet-hot-added part of the
> memory backend.
>
> Co-developed-by: David Hildenbrand <david@redhat.com>
> Acked-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Hi; I was looking at this code because Coverity reported an
issue in it. I think that's because Coverity has got confused
about the way you're doing memory allocation here. But
in looking at the code I see that you're using alloca() in
this function.
Please could you rewrite this not to do that -- we don't use
alloca() or variable-length-arrays in QEMU except in a few
cases which we're trying to get rid of, so we'd like not to
add new uses to the code base.
> +static void hv_balloon_hot_add_posting(HvBalloon *balloon, StateDesc *stdesc)
> +{
> + PageRange *hot_add_range = &balloon->hot_add_range;
> + uint64_t *current_count = &balloon->ha_current_count;
> + VMBusChannel *chan = hv_balloon_get_channel(balloon);
> + struct dm_hot_add *ha;
> + size_t ha_size = sizeof(*ha) + sizeof(ha->range);
> + union dm_mem_page_range *ha_region;
> + uint64_t align, chunk_max_size;
> + ssize_t ret;
> +
> + assert(balloon->state == S_HOT_ADD_POSTING);
> + assert(hot_add_range->count > 0);
> +
> + align = (1 << balloon->caps.cap_bits.hot_add_alignment) *
> + (MiB / HV_BALLOON_PAGE_SIZE);
> + if (align >= HV_BALLOON_HA_CHUNK_PAGES) {
> + /*
> + * If the required alignment is higher than the chunk size we let it
> + * override that size.
> + */
> + chunk_max_size = align;
> + } else {
> + chunk_max_size = QEMU_ALIGN_DOWN(HV_BALLOON_HA_CHUNK_PAGES, align);
> + }
> +
> + /*
> + * hot_add_range->count starts aligned in hv_balloon_hot_add_setup(),
> + * then it is either reduced by subtracting aligned current_count or
> + * further hot-adds are prevented by marking the whole remaining our range
> + * as unusable in hv_balloon_handle_hot_add_response().
> + */
> + *current_count = MIN(hot_add_range->count, chunk_max_size);
> +
> + ha = alloca(ha_size);
> + ha_region = &(&ha->range)[1];
> + memset(ha, 0, ha_size);
> + ha->hdr.type = DM_MEM_HOT_ADD_REQUEST;
> + ha->hdr.size = ha_size;
> + ha->hdr.trans_id = balloon->trans_id;
> +
> + ha->range.finfo.start_page = hot_add_range->start;
> + ha->range.finfo.page_cnt = *current_count;
> + ha_region->finfo.start_page = hot_add_range->start;
> + ha_region->finfo.page_cnt = ha->range.finfo.page_cnt;
> +
> + trace_hv_balloon_outgoing_hot_add(ha->hdr.trans_id,
> + *current_count, hot_add_range->start);
> +
> + ret = vmbus_channel_send(chan, VMBUS_PACKET_DATA_INBAND,
> + NULL, 0, ha, ha_size, false,
> + ha->hdr.trans_id);
> + if (ret <= 0) {
> + error_report("error %zd when posting hot add msg, expect problems",
> + ret);
> + }
> +
> + HV_BALLOON_STATE_DESC_SET(stdesc, S_HOT_ADD_REPLY_WAIT);
> +}
thanks
-- PMM
On 9.11.2023 15:51, Peter Maydell wrote: > On Mon, 6 Nov 2023 at 14:23, Maciej S. Szmigiero > <mail@maciej.szmigiero.name> wrote: >> >> From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com> >> >> One of advantages of using this protocol over ACPI-based PC DIMM hotplug is >> that it allows hot-adding memory in much smaller granularity because the >> ACPI DIMM slot limit does not apply. >> >> In order to enable this functionality a new memory backend needs to be >> created and provided to the driver via the "memdev" parameter. >> >> This can be achieved by, for example, adding >> "-object memory-backend-ram,id=mem1,size=32G" to the QEMU command line and >> then instantiating the driver with "memdev=mem1" parameter. >> >> The device will try to use multiple memslots to cover the memory backend in >> order to reduce the size of metadata for the not-yet-hot-added part of the >> memory backend. >> >> Co-developed-by: David Hildenbrand <david@redhat.com> >> Acked-by: David Hildenbrand <david@redhat.com> >> Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com> > > Hi; I was looking at this code because Coverity reported an > issue in it. I think that's because Coverity has got confused > about the way you're doing memory allocation here. But > in looking at the code I see that you're using alloca() in > this function. > > Please could you rewrite this not to do that -- we don't use > alloca() or variable-length-arrays in QEMU except in a few > cases which we're trying to get rid of, so we'd like not to > add new uses to the code base. > Sure, will do - I didn't know alloca() is frowned upon (and David probably didn't either). > thanks > -- PMM Thanks, Maciej
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