From: Jason Wang Date: Fri, 4 Mar 2016 11:24:52 +0000 (-0500) Subject: vhost: introduce vhost_vq_avail_empty() X-Git-Tag: v4.14-rc1~3598^2~2 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=d4a60603fa0b42012decfa058dfa44cffde7a10c;p=platform%2Fkernel%2Flinux-rpi.git 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 Signed-off-by: Michael S. Tsirkin --- diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 596de21..97f26f0 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 eef33b11..af5af77 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,