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