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: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index c8c25db..6eb1525 100644 (file)
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -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",