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Commit d4a60603 authored by Jason Wang's avatar Jason Wang Committed by Michael S. Tsirkin
Browse files

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: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 526d3e7f

drivers/vhost/vhost.c

+14 −0
Original line number Diff line number Diff line
@@ -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)

{

drivers/vhost/vhost.h

+1 −0
Original line number Diff line number Diff line
@@ -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,