Documentation/memory-barriers.txt says:
Mandatory barriers should not be used to control SMP effects, since
mandatory barriers unnecessarily impose overhead on UP systems.
This rule applies to virtio, so let's do it correctly.
Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
---
drivers/virtio/virtio_ring.c | 12 ++++++------
1 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index fbd2ecd..2216587 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -36,10 +36,10 @@
panic("%s:in_use = %i\n", \
(_vq)->vq.name, (_vq)->in_use); \
(_vq)->in_use = __LINE__; \
- mb(); \
+ smp_mb(); \
} while (0)
#define END_USE(_vq) \
- do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; mb(); } while(0)
+ do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; smp_mb(); } while(0)
#else
#define BAD_RING(_vq, fmt, args...) \
do { \
@@ -221,13 +221,13 @@ static void vring_kick(struct virtqueue *_vq)
START_USE(vq);
/* Descriptors and available array need to be set before we expose the
* new available array entries. */
- wmb();
+ smp_wmb();
vq->vring.avail->idx += vq->num_added;
vq->num_added = 0;
/* Need to update avail index before checking if we should notify */
- mb();
+ smp_mb();
if (!(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY))
/* Prod other side to tell it about changes. */
@@ -286,7 +286,7 @@ static void *vring_get_buf(struct virtqueue *_vq, unsigned
int *len)
}
/* Only get used array entries after they have been exposed by host. */
- rmb();
+ smp_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;
@@ -324,7 +324,7 @@ static bool vring_enable_cb(struct virtqueue *_vq)
/* We optimistically turn back on interrupts, then check if there was
* more to do. */
vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
- mb();
+ smp_mb();
if (unlikely(more_used(vq))) {
END_USE(vq);
return false;
--
1.6.6.144.g5c3af
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