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virtio: use virtio accessor to access packed descriptor flags 

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

So this patch switches to use virito_{stw|lduw}_phys_cached() to make
sure the aceess is atomic.

Fixes: 86044b24e8 ("virtio: basic packed virtqueue support")
Cc: qemu-stable@nongnu.org
Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20211111063854.29060-1-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>
master
Jason Wang 2021-11-11 14:38:53 +08:00 committed by Michael S. Tsirkin
parent 7e6055c99f
commit f463e761a4
1 changed files with 4 additions and 7 deletions
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11
hw/virtio/virtio.c
View File

@ -507,11 +507,9 @@ static void vring_packed_desc_read_flags(VirtIODevice *vdev,
MemoryRegionCache *cache,
int i)
{
address_space_read_cached(cache,
i * sizeof(VRingPackedDesc) +
offsetof(VRingPackedDesc, flags),
flags, sizeof(*flags));
virtio_tswap16s(vdev, flags);
hwaddr off = i * sizeof(VRingPackedDesc) + offsetof(VRingPackedDesc, flags);
*flags = virtio_lduw_phys_cached(vdev, cache, off);
}
static void vring_packed_desc_read(VirtIODevice *vdev,
@ -564,8 +562,7 @@ static void vring_packed_desc_write_flags(VirtIODevice *vdev,
{
hwaddr off = i * sizeof(VRingPackedDesc) + offsetof(VRingPackedDesc, flags);
virtio_tswap16s(vdev, &desc->flags);
address_space_write_cached(cache, off, &desc->flags, sizeof(desc->flags));
virtio_stw_phys_cached(vdev, cache, off, desc->flags);
address_space_cache_invalidate(cache, off, sizeof(desc->flags));
}