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virtio_net: fix PAGE_SIZE > 64k

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I don't have any guests with PAGE_SIZE > 64k but the
code seems to be clearly broken in that case
as PAGE_SIZE / MERGEABLE_BUFFER_ALIGN will need
more than 8 bit and so the code in mergeable_ctx_to_buf_address
does not give us the actual true size.

Cc: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Michael S. Tsirkin 2017-01-23 21:37:52 +02:00 committed by David S. Miller
parent 0fb44559ff
commit d0fa28f000
1 changed files with 9 additions and 1 deletions
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10
drivers/net/virtio_net.c
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@ -48,8 +48,16 @@ module_param(gso, bool, 0444);
*/
DECLARE_EWMA(pkt_len, 1, 64)
/* With mergeable buffers we align buffer address and use the low bits to
* encode its true size. Buffer size is up to 1 page so we need to align to
* square root of page size to ensure we reserve enough bits to encode the true
* size.
*/
#define MERGEABLE_BUFFER_MIN_ALIGN_SHIFT ((PAGE_SHIFT + 1) / 2)
/* Minimum alignment for mergeable packet buffers. */
#define MERGEABLE_BUFFER_ALIGN max(L1_CACHE_BYTES, 256)
#define MERGEABLE_BUFFER_ALIGN max(L1_CACHE_BYTES, \
1 << MERGEABLE_BUFFER_MIN_ALIGN_SHIFT)
#define VIRTNET_DRIVER_VERSION "1.0.0"