linux-kernel - Re: [PATCH v2] virtio_balloon: Fix endless deflation and inflation on arm64

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <53ec0cfb-37c8-f8e3-4cd3-53a390b2cd2b@redhat.com>
Date:   Mon, 2 Oct 2023 13:50:45 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Gavin Shan <gshan@...hat.com>,
        virtualization@...ts.linux-foundation.org, mst@...hat.com
Cc:     xuanzhuo@...ux.alibaba.com, linux-kernel@...r.kernel.org,
        zhenyzha@...hat.com, shan.gavin@...il.com
Subject: Re: [PATCH v2] virtio_balloon: Fix endless deflation and inflation on
 arm64

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@...hat.com>
>> Tested-by: Zhenyu Zhang <zhenyzha@...hat.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