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virtio: support unlocked queue kick
Based on patch by Christoph for virtio_blk speedup:
Split virtqueue_kick to be able to do the actual notification
outside the lock protecting the virtqueue. This patch was
originally done by Stefan Hajnoczi, but I can't find the
original one anymore and had to recreated it from memory.
Pointers to the original or corrections for the commit message
are welcome.
Stefan's patch was here:
a6d06644e3
http://www.spinics.net/lists/linux-virtualization/msg14616.html
Third time's the charm!
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
parent
f96fde41f7
commit
41f0377f73
@ -262,19 +262,22 @@ add_head:
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EXPORT_SYMBOL_GPL(virtqueue_add_buf);
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/**
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* virtqueue_kick - update after add_buf
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* virtqueue_kick_prepare - first half of split virtqueue_kick call.
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* @vq: the struct virtqueue
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*
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* After one or more virtqueue_add_buf calls, invoke this to kick
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* the other side.
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* Instead of virtqueue_kick(), you can do:
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* if (virtqueue_kick_prepare(vq))
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* virtqueue_notify(vq);
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*
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* Caller must ensure we don't call this with other virtqueue
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* operations at the same time (except where noted).
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* This is sometimes useful because the virtqueue_kick_prepare() needs
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* to be serialized, but the actual virtqueue_notify() call does not.
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*/
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void virtqueue_kick(struct virtqueue *_vq)
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bool virtqueue_kick_prepare(struct virtqueue *_vq)
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{
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struct vring_virtqueue *vq = to_vvq(_vq);
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u16 new, old;
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bool needs_kick;
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START_USE(vq);
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/* Descriptors and available array need to be set before we expose the
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* new available array entries. */
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@ -287,13 +290,46 @@ void virtqueue_kick(struct virtqueue *_vq)
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/* Need to update avail index before checking if we should notify */
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virtio_mb(vq);
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if (vq->event ?
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vring_need_event(vring_avail_event(&vq->vring), new, old) :
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!(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY))
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/* Prod other side to tell it about changes. */
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vq->notify(&vq->vq);
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if (vq->event) {
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needs_kick = vring_need_event(vring_avail_event(&vq->vring),
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new, old);
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} else {
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needs_kick = !(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY);
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}
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END_USE(vq);
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return needs_kick;
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}
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EXPORT_SYMBOL_GPL(virtqueue_kick_prepare);
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/**
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* virtqueue_notify - second half of split virtqueue_kick call.
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* @vq: the struct virtqueue
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*
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* This does not need to be serialized.
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*/
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void virtqueue_notify(struct virtqueue *_vq)
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{
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struct vring_virtqueue *vq = to_vvq(_vq);
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/* Prod other side to tell it about changes. */
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vq->notify(_vq);
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}
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EXPORT_SYMBOL_GPL(virtqueue_notify);
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/**
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* virtqueue_kick - update after add_buf
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* @vq: the struct virtqueue
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*
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* After one or more virtqueue_add_buf calls, invoke this to kick
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* the other side.
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*
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* Caller must ensure we don't call this with other virtqueue
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* operations at the same time (except where noted).
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*/
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void virtqueue_kick(struct virtqueue *vq)
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{
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if (virtqueue_kick_prepare(vq))
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virtqueue_notify(vq);
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}
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EXPORT_SYMBOL_GPL(virtqueue_kick);
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@ -34,6 +34,10 @@ int virtqueue_add_buf(struct virtqueue *vq,
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void virtqueue_kick(struct virtqueue *vq);
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bool virtqueue_kick_prepare(struct virtqueue *vq);
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void virtqueue_notify(struct virtqueue *vq);
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void *virtqueue_get_buf(struct virtqueue *vq, unsigned int *len);
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void virtqueue_disable_cb(struct virtqueue *vq);
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