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virtio_balloon: Fix endless deflation and inflation on arm64

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commit 07622bd415639e9709579f400afd19e7e9866e5e upstream.

The deflation request to the target, which isn't unaligned to the
guest page size causes endless deflation and inflation actions. For
example, we receive the flooding QMP events for the changes on memory
balloon's size after a deflation request to the unaligned target is
sent for the ARM64 guest, where we have 64KB base page size.

  /home/gavin/sandbox/qemu.main/build/qemu-system-aarch64      \
  -accel kvm -machine virt,gic-version=host -cpu host          \
  -smp maxcpus=8,cpus=8,sockets=2,clusters=2,cores=2,threads=1 \
  -m 1024M,slots=16,maxmem=64G                                 \
  -object memory-backend-ram,id=mem0,size=512M                 \
  -object memory-backend-ram,id=mem1,size=512M                 \
  -numa node,nodeid=0,memdev=mem0,cpus=0-3                     \
  -numa node,nodeid=1,memdev=mem1,cpus=4-7                     \
    :                                                          \
  -device virtio-balloon-pci,id=balloon0,bus=pcie.10

  { "execute" : "balloon", "arguments": { "value" : 1073672192 } }
  {"return": {}}
  {"timestamp": {"seconds": 1693272173, "microseconds": 88667},   \
   "event": "BALLOON_CHANGE", "data": {"actual": 1073610752}}
  {"timestamp": {"seconds": 1693272174, "microseconds": 89704},   \
   "event": "BALLOON_CHANGE", "data": {"actual": 1073610752}}
  {"timestamp": {"seconds": 1693272175, "microseconds": 90819},   \
   "event": "BALLOON_CHANGE", "data": {"actual": 1073610752}}
  {"timestamp": {"seconds": 1693272176, "microseconds": 91961},   \
   "event": "BALLOON_CHANGE", "data": {"actual": 1073610752}}
  {"timestamp": {"seconds": 1693272177, "microseconds": 93040},   \
   "event": "BALLOON_CHANGE", "data": {"actual": 1073676288}}
  {"timestamp": {"seconds": 1693272178, "microseconds": 94117},   \
   "event": "BALLOON_CHANGE", "data": {"actual": 1073676288}}
  {"timestamp": {"seconds": 1693272179, "microseconds": 95337},   \
   "event": "BALLOON_CHANGE", "data": {"actual": 1073610752}}
  {"timestamp": {"seconds": 1693272180, "microseconds": 96615},   \
   "event": "BALLOON_CHANGE", "data": {"actual": 1073676288}}
  {"timestamp": {"seconds": 1693272181, "microseconds": 97626},   \
   "event": "BALLOON_CHANGE", "data": {"actual": 1073610752}}
  {"timestamp": {"seconds": 1693272182, "microseconds": 98693},   \
   "event": "BALLOON_CHANGE", "data": {"actual": 1073676288}}
  {"timestamp": {"seconds": 1693272183, "microseconds": 99698},   \
   "event": "BALLOON_CHANGE", "data": {"actual": 1073610752}}
  {"timestamp": {"seconds": 1693272184, "microseconds": 100727},  \
   "event": "BALLOON_CHANGE", "data": {"actual": 1073610752}}
  {"timestamp": {"seconds": 1693272185, "microseconds": 90430},   \
   "event": "BALLOON_CHANGE", "data": {"actual": 1073610752}}
  {"timestamp": {"seconds": 1693272186, "microseconds": 102999},  \
   "event": "BALLOON_CHANGE", "data": {"actual": 1073676288}}
     :
  <The similar QMP events repeat>

Fix it by aligning the target up to the guest page size, 64KB in this
specific case. With this applied, no flooding QMP events are observed
and the memory balloon's size can be stablizied to 0x3ffe0000 soon
after the deflation request is sent.

  { "execute" : "balloon", "arguments": { "value" : 1073672192 } }
  {"return": {}}
  {"timestamp": {"seconds": 1693273328, "microseconds": 793075},  \
   "event": "BALLOON_CHANGE", "data": {"actual": 1073610752}}
  { "execute" : "query-balloon" }
  {"return": {"actual": 1073610752}}

Cc: stable@vger.kernel.org
Signed-off-by: Gavin Shan <gshan@redhat.com>
Tested-by: Zhenyu Zhang <zhenyzha@redhat.com>
Message-Id: <20230831011007.1032822-1-gshan@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Gavin Shan 2023-08-31 11:10:07 +10:00 committed by Greg Kroah-Hartman
parent be84e96426
commit 8d394fcb03
1 changed files with 5 additions and 1 deletions
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6
drivers/virtio/virtio_balloon.c
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@ -365,7 +365,11 @@ static inline s64 towards_target(struct virtio_balloon *vb)
if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1)) if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
num_pages = le32_to_cpu((__force __le32)num_pages); num_pages = le32_to_cpu((__force __le32)num_pages);
target = num_pages; /*
* Aligned up to guest page size to avoid inflating and deflating
* balloon endlessly.
*/
target = ALIGN(num_pages, VIRTIO_BALLOON_PAGES_PER_PAGE);
return target - vb->num_pages; return target - vb->num_pages;
} }