From: Gavin Shan <gshan@redhat.com>
To: virtualization@lists.linux.dev
Cc: linux-kernel@vger.kernel.org, mst@redhat.com,
jasowang@redhat.com, davem@davemloft.net, stefanha@redhat.com,
sgarzare@redhat.com, keirf@google.com, yihyu@redhat.com,
shan.gavin@gmail.com
Subject: [PATCH v2 0/2] vhost: Fix stale available ring entries
Date: Wed, 27 Mar 2024 09:38:44 +1000 [thread overview]
Message-ID: <20240326233846.1086253-1-gshan@redhat.com> (raw)
The issue was reported by Yihuang Yu on NVidia's grace-hopper (ARM64)
platform. The wrong head (available ring entry) is seen by the guest
when running 'netperf' on the guest and running 'netserver' on another
NVidia's grace-grace machine.
/home/gavin/sandbox/qemu.main/build/qemu-system-aarch64 \
-accel kvm -machine virt,gic-version=host -cpu host \
-smp maxcpus=1,cpus=1,sockets=1,clusters=1,cores=1,threads=1 \
-m 4096M,slots=16,maxmem=64G \
-object memory-backend-ram,id=mem0,size=4096M \
: \
-netdev tap,id=tap0,vhost=true \
-device virtio-net-pci,bus=pcie.8,netdev=tap0,mac=52:54:00:f1:26:b0
:
guest# ifconfig eth0 | grep 'inet addr'
inet addr:10.26.1.220
guest# netperf -H 10.26.1.81 -l 60 -C -c -t UDP_STREAM
virtio_net virtio0: output.0:id 100 is not a head!
There is missed smp_rmb() in vhost_vq_avail_empty() and vhost_enable_notify().
Without smp_rmb(), vq->avail_idx is increased but the available ring
entries aren't arriving to vhost side yet. So a stale available ring
entry can be fetched in vhost_get_vq_desc().
Fix it by adding smp_rmb() in those two functions. Note that I need
two patches so that they can be easily picked up by the stable kernel.
With the changes, I'm unable to hit the issue again.
Gavin Shan (2):
vhost: Add smp_rmb() in vhost_vq_avail_empty()
vhost: Add smp_rmb() in vhost_enable_notify()
drivers/vhost/vhost.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)
--
2.44.0
next reply other threads:[~2024-03-26 23:39 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-26 23:38 Gavin Shan [this message]
2024-03-26 23:38 ` [PATCH v2 1/2] vhost: Add smp_rmb() in vhost_vq_avail_empty() Gavin Shan
2024-03-27 2:34 ` Jason Wang
2024-03-27 2:44 ` Jason Wang
2024-03-27 4:08 ` Gavin Shan
2024-03-27 7:35 ` Gavin Shan
2024-03-27 7:42 ` Jason Wang
2024-03-28 0:27 ` Gavin Shan
2024-03-27 12:07 ` Michael S. Tsirkin
2024-03-28 0:26 ` Gavin Shan
2024-03-26 23:38 ` [PATCH v2 2/2] vhost: Add smp_rmb() in vhost_enable_notify() Gavin Shan
2024-03-27 2:41 ` Jason Wang
2024-03-27 4:10 ` Gavin Shan
2024-03-26 23:55 ` [PATCH v2 0/2] vhost: Fix stale available ring entries Gavin Shan
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