Commit 2d61ba95 authored Oct 25, 2009 by Michael S. Tsirkin Committed by Rusty Russell Oct 29, 2009

virtio: order used ring after used index read



On SMP guests, reads from the ring might bypass used index reads. This
causes guest crashes because host writes to used index to signal ring
data readiness.  Fix this by inserting rmb before used ring reads.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: stable@kernel.org

parent 0b22bd0b

drivers/virtio/virtio_ring.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -285,6 +285,9 @@ static void vring_get_buf(struct virtqueue _vq, unsigned int *len)
		return NULL;
		}

		/* Only get used array entries after they have been exposed by host. */
		rmb();

		i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id;
		*len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len;