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SubjectRe: [PATCH v2] virtio_balloon: Fix endless deflation and inflation on arm64
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On 25.09.23 01:58, Gavin Shan wrote:
> Hi David and Michael,
>
> On 8/31/23 11:10, Gavin Shan wrote:
>> 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}}
>>
>> Signed-off-by: Gavin Shan <gshan@redhat.com>
>> Tested-by: Zhenyu Zhang <zhenyzha@redhat.com>
>> ---
>> v2: Align @num_pages up to the guest page size in towards_target()
>> directly as David suggested.
>> ---
>> drivers/virtio/virtio_balloon.c | 6 +++++-
>> 1 file changed, 5 insertions(+), 1 deletion(-)
>>
>
> If the patch looks good, could you please merge this to Linux 6.6.rc4 since
> it's something needed by our downstream. I hope it can land upstream as early
> as possible, thanks a lot.

@MST, I cannot spot it in your usual vhost git yet. Should I pick it up
or what are your plans?

--
Cheers,

David / dhildenb

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