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| author | Jason Wang <jasowang@redhat.com> | 2016-03-04 06:24:52 -0500 |
|---|---|---|
| committer | Michael S. Tsirkin <mst@redhat.com> | 2016-03-11 02:18:50 +0200 |
| commit | d4a60603fa0b42012decfa058dfa44cffde7a10c (patch) | |
| tree | e67544642fc442b1c3823a4cef4a744cc8e81bf1 /drivers/vhost | |
| parent | 526d3e7ff515582eaf7cf5d9da2a11bf681204e6 (diff) | |
| download | linux-d4a60603fa0b42012decfa058dfa44cffde7a10c.tar.bz2 | |
vhost: introduce vhost_vq_avail_empty()
This patch introduces a helper which will return true if we're sure
that the available ring is empty for a specific vq. When we're not
sure, e.g vq access failure, return false instead. This could be used
for busy polling code to exit the busy loop.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'drivers/vhost')
| -rw-r--r-- | drivers/vhost/vhost.c | 14 | ||||
| -rw-r--r-- | drivers/vhost/vhost.h | 1 |
2 files changed, 15 insertions, 0 deletions
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 596de212fe7e..97f26f0aab40 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1658,6 +1658,20 @@ void vhost_add_used_and_signal_n(struct vhost_dev *dev, } EXPORT_SYMBOL_GPL(vhost_add_used_and_signal_n); +/* return true if we're sure that avaiable ring is empty */ +bool vhost_vq_avail_empty(struct vhost_dev *dev, struct vhost_virtqueue *vq) +{ + __virtio16 avail_idx; + int r; + + r = __get_user(avail_idx, &vq->avail->idx); + if (r) + return false; + + return vhost16_to_cpu(vq, avail_idx) == vq->avail_idx; +} +EXPORT_SYMBOL_GPL(vhost_vq_avail_empty); + /* OK, now we need to know about added descriptors. */ bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq) { diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h index eef33b11a7ed..af5af773bf7a 100644 --- a/drivers/vhost/vhost.h +++ b/drivers/vhost/vhost.h @@ -159,6 +159,7 @@ void vhost_add_used_and_signal_n(struct vhost_dev *, struct vhost_virtqueue *, struct vring_used_elem *heads, unsigned count); void vhost_signal(struct vhost_dev *, struct vhost_virtqueue *); void vhost_disable_notify(struct vhost_dev *, struct vhost_virtqueue *); +bool vhost_vq_avail_empty(struct vhost_dev *, struct vhost_virtqueue *); bool vhost_enable_notify(struct vhost_dev *, struct vhost_virtqueue *); int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log, |