From: Christoph Hellwig <hch@xxxxxx> 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. Signed-off-by: Christoph Hellwig <hch@xxxxxx> Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> --- drivers/virtio/virtio_ring.c | 33 ++++++++++++++++++++++++++------- include/linux/virtio.h | 21 +++++++++++++++++++++ 2 files changed, 47 insertions(+), 7 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index c7a2c20..c5f0458 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -238,10 +238,12 @@ add_head: } EXPORT_SYMBOL_GPL(virtqueue_add_buf_gfp); -void virtqueue_kick(struct virtqueue *_vq) +bool virtqueue_kick_prepare(struct virtqueue *_vq) { struct vring_virtqueue *vq = to_vvq(_vq); u16 new, old; + bool needs_kick; + START_USE(vq); /* Descriptors and available array need to be set before we expose the * new available array entries. */ @@ -254,13 +256,30 @@ void virtqueue_kick(struct virtqueue *_vq) /* Need to update avail index before checking if we should notify */ virtio_mb(); - if (vq->event ? - vring_need_event(vring_avail_event(&vq->vring), new, old) : - !(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY)) - /* Prod other side to tell it about changes. */ - vq->notify(&vq->vq); - + if (vq->event) { + needs_kick = vring_need_event(vring_avail_event(&vq->vring), + new, old); + } else { + needs_kick = (!(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY)); + } END_USE(vq); + return needs_kick; +} +EXPORT_SYMBOL_GPL(virtqueue_kick_prepare); + +void virtqueue_notify(struct virtqueue *_vq) +{ + struct vring_virtqueue *vq = to_vvq(_vq); + + /* Prod other side to tell it about changes. */ + vq->notify(_vq); +} +EXPORT_SYMBOL_GPL(virtqueue_notify); + +void virtqueue_kick(struct virtqueue *vq) +{ + if (virtqueue_kick_prepare(vq)) + virtqueue_notify(vq); } EXPORT_SYMBOL_GPL(virtqueue_kick); diff --git a/include/linux/virtio.h b/include/linux/virtio.h index 4c069d8..722a35d 100644 --- a/include/linux/virtio.h +++ b/include/linux/virtio.h @@ -90,6 +90,27 @@ static inline int virtqueue_add_buf(struct virtqueue *vq, void virtqueue_kick(struct virtqueue *vq); +/** + * virtqueue_kick_prepare - first half of split virtqueue_kick call. + * @vq: the struct virtqueue + * + * Instead of virtqueue_kick(), you can do: + * if (virtqueue_kick_prepare(vq)) + * virtqueue_notify(vq); + * + * This is sometimes useful because the virtqueue_kick_prepare() needs + * to be serialized, but the actual virtqueue_notify() call does not. + */ +bool virtqueue_kick_prepare(struct virtqueue *vq); + +/** + * virtqueue_notify - second half of split virtqueue_kick call. + * @vq: the struct virtqueue + * + * This does not need to be serialized. + */ +void virtqueue_notify(struct virtqueue *vq); + void *virtqueue_get_buf(struct virtqueue *vq, unsigned int *len); void virtqueue_disable_cb(struct virtqueue *vq); -- 1.7.6.4 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html