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virtio: use virtio accessor to access packed event

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We used to access packed descriptor event and off_wrap via
address_space_{write|read}_cached(). When we hit the cache, memcpy()
is used which is not atomic which may lead a wrong value to be read or
wrote.

This patch fixes this by switching to use
virito_{stw|lduw}_phys_cached() to make sure the access is atomic.

Fixes: 683f766567 ("virtio: event suppression support for packed ring")
Cc: qemu-stable@nongnu.org
Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20211111063854.29060-2-jasowang@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Jason Wang 2021-11-11 14:38:54 +08:00 committed by Michael S. Tsirkin
parent f463e761a4
commit d152cdd6f6
1 changed files with 4 additions and 9 deletions
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13
hw/virtio/virtio.c
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@ -247,13 +247,10 @@ static void vring_packed_event_read(VirtIODevice *vdev,
hwaddr off_off = offsetof(VRingPackedDescEvent, off_wrap);
hwaddr off_flags = offsetof(VRingPackedDescEvent, flags);
address_space_read_cached(cache, off_flags, &e->flags,
sizeof(e->flags));
e->flags = virtio_lduw_phys_cached(vdev, cache, off_flags);
/* Make sure flags is seen before off_wrap */
smp_rmb();
address_space_read_cached(cache, off_off, &e->off_wrap,
sizeof(e->off_wrap));
virtio_tswap16s(vdev, &e->off_wrap);
e->off_wrap = virtio_lduw_phys_cached(vdev, cache, off_off);
virtio_tswap16s(vdev, &e->flags);
}
@ -263,8 +260,7 @@ static void vring_packed_off_wrap_write(VirtIODevice *vdev,
{
hwaddr off = offsetof(VRingPackedDescEvent, off_wrap);
virtio_tswap16s(vdev, &off_wrap);
address_space_write_cached(cache, off, &off_wrap, sizeof(off_wrap));
virtio_stw_phys_cached(vdev, cache, off, off_wrap);
address_space_cache_invalidate(cache, off, sizeof(off_wrap));
}
@ -273,8 +269,7 @@ static void vring_packed_flags_write(VirtIODevice *vdev,
{
hwaddr off = offsetof(VRingPackedDescEvent, flags);
virtio_tswap16s(vdev, &flags);
address_space_write_cached(cache, off, &flags, sizeof(flags));
virtio_stw_phys_cached(vdev, cache, off, flags);
address_space_cache_invalidate(cache, off, sizeof(flags));
}