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([2001:8003:e5b0:9f00:dbbc:1945:6e65:ec5]) by smtp.gmail.com with ESMTPSA id y9-20020a17090a16c900b002772faee740sm1216900pje.5.2023.09.24.16.58.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 24 Sep 2023 16:58:40 -0700 (PDT) Message-ID: <9efb4685-7c28-d51d-fd5b-aa2de8e5ded2@redhat.com> Date: Mon, 25 Sep 2023 09:58:35 +1000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH v2] virtio_balloon: Fix endless deflation and inflation on arm64 Content-Language: en-US From: Gavin Shan To: virtualization@lists.linux-foundation.org Cc: xuanzhuo@linux.alibaba.com, mst@redhat.com, linux-kernel@vger.kernel.org, zhenyzha@redhat.com, shan.gavin@gmail.com, David Hildenbrand References: <20230831011007.1032822-1-gshan@redhat.com> In-Reply-To: <20230831011007.1032822-1-gshan@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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}} > : > > > 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 > Tested-by: Zhenyu Zhang > --- > 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. > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > index 5b15936a5214..2d5d252ef419 100644 > --- a/drivers/virtio/virtio_balloon.c > +++ b/drivers/virtio/virtio_balloon.c > @@ -395,7 +395,11 @@ static inline s64 towards_target(struct virtio_balloon *vb) > virtio_cread_le(vb->vdev, struct virtio_balloon_config, num_pages, > &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; > } > Thanks, Gavin