Commit 5659338c authored by Michael S. Tsirkin's avatar Michael S. Tsirkin Committed by David S. Miller
Browse files

vhost-net: switch to smp barriers 



vhost-net only uses memory barriers to control SMP effects
(communication with userspace potentially running on a different CPU),
so it should use SMP barriers and not mandatory barriers for memory
access ordering, as suggested by Documentation/memory-barriers.txt

Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Acked-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f10a1f2e

drivers/vhost/vhost.c

+5 −5
Original line number Diff line number Diff line
@@ -685,7 +685,7 @@ int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log, 
	int i, r;



	/* Make sure data written is seen before log. */

	wmb();

	smp_wmb();

	for (i = 0; i < log_num; ++i) {

		u64 l = min(log[i].len, len);

		r = log_write(vq->log_base, log[i].addr, l);
@@ -884,7 +884,7 @@ unsigned vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq, 
		return vq->num;



	/* Only get avail ring entries after they have been exposed by guest. */

	rmb();

	smp_rmb();



	/* Grab the next descriptor number they're advertising, and increment

	 * the index we've seen. */
@@ -996,14 +996,14 @@ int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len) 
		return -EFAULT;

	}

	/* Make sure buffer is written before we update index. */

	wmb();

	smp_wmb();

	if (put_user(vq->last_used_idx + 1, &vq->used->idx)) {

		vq_err(vq, "Failed to increment used idx");

		return -EFAULT;

	}

	if (unlikely(vq->log_used)) {

		/* Make sure data is seen before log. */

		wmb();

		smp_wmb();

		log_write(vq->log_base, vq->log_addr + sizeof *vq->used->ring *

			  (vq->last_used_idx % vq->num),

			  sizeof *vq->used->ring);
@@ -1060,7 +1060,7 @@ bool vhost_enable_notify(struct vhost_virtqueue *vq) 
	}

	/* They could have slipped one in as we were doing that: make

	 * sure it's written, then check again. */

	mb();

	smp_mb();

	r = get_user(avail_idx, &vq->avail->idx);

	if (r) {

		vq_err(vq, "Failed to check avail idx at %p: %d\n",

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