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| author | Michael S. Tsirkin <mst@redhat.com> | 2015-12-17 11:20:39 +0100 |
|---|---|---|
| committer | Michael S. Tsirkin <mst@redhat.com> | 2016-01-12 19:47:02 +0100 |
| commit | 788e5b3a5da24cc8d93ce2f7c6508181cd7d7fb6 (patch) | |
| tree | 7e54e74c3f7373a04780ad14cb157089c76abeb2 | |
| parent | sh: move xchg_cmpxchg to a header by itself (diff) | |
| download | linux-788e5b3a5da24cc8d93ce2f7c6508181cd7d7fb6.tar.xz linux-788e5b3a5da24cc8d93ce2f7c6508181cd7d7fb6.zip | |
virtio_ring: use virt_store_mb
We need a full barrier after writing out event index, using
virt_store_mb there seems better than open-coding. As usual, we need a
wrapper to account for strong barriers.
It's tempting to use this in vhost as well, for that, we'll
need a variant of smp_store_mb that works on __user pointers.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
| -rw-r--r-- | drivers/virtio/virtio_ring.c | 15 | ||||
| -rw-r--r-- | include/linux/virtio_ring.h | 11 |
2 files changed, 20 insertions, 6 deletions
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index ee663c458b20..e12e385f7ac3 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -517,10 +517,10 @@ void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len) /* If we expect an interrupt for the next entry, tell host * by writing event index and flush out the write before * the read in the next get_buf call. */ - if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) { - vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev, vq->last_used_idx); - virtio_mb(vq->weak_barriers); - } + if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) + virtio_store_mb(vq->weak_barriers, + &vring_used_event(&vq->vring), + cpu_to_virtio16(_vq->vdev, vq->last_used_idx)); #ifdef DEBUG vq->last_add_time_valid = false; @@ -653,8 +653,11 @@ bool virtqueue_enable_cb_delayed(struct virtqueue *_vq) } /* TODO: tune this threshold */ bufs = (u16)(vq->avail_idx_shadow - vq->last_used_idx) * 3 / 4; - vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev, vq->last_used_idx + bufs); - virtio_mb(vq->weak_barriers); + + virtio_store_mb(vq->weak_barriers, + &vring_used_event(&vq->vring), + cpu_to_virtio16(_vq->vdev, vq->last_used_idx + bufs)); + if (unlikely((u16)(virtio16_to_cpu(_vq->vdev, vq->vring.used->idx) - vq->last_used_idx) > bufs)) { END_USE(vq); return false; diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h index f3fa55bdd6ce..a156e2b6ccfe 100644 --- a/include/linux/virtio_ring.h +++ b/include/linux/virtio_ring.h @@ -45,6 +45,17 @@ static inline void virtio_wmb(bool weak_barriers) wmb(); } +static inline void virtio_store_mb(bool weak_barriers, + __virtio16 *p, __virtio16 v) +{ + if (weak_barriers) { + virt_store_mb(*p, v); + } else { + WRITE_ONCE(*p, v); + mb(); + } +} + struct virtio_device; struct virtqueue; |