In vhost_enable_notify() we enable the notifications and we read the avail index to check if new buffers have become available in the meantime. We are not caching the avail index, so when the device will call vhost_get_vq_desc(), it will find the old value in the cache and it will read the avail index again. It would be better to refresh the cache every time we read avail index, so let's change vhost_enable_notify() caching the value in `avail_idx` and compare it with `last_avail_idx` to check if there are new buffers available. Anyway, we don't expect a significant performance boost because the above path is not very common, indeed vhost_enable_notify() is often called with unlikely(), expecting that avail index has not been updated. Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx> --- v1: - improved the commit description [MST, Jason] --- drivers/vhost/vhost.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 59edb5a1ffe2..07363dff559e 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -2543,8 +2543,9 @@ bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq) &vq->avail->idx, r); return false; } + vq->avail_idx = vhost16_to_cpu(vq, avail_idx); - return vhost16_to_cpu(vq, avail_idx) != vq->avail_idx; + return vq->avail_idx != vq->last_avail_idx; } EXPORT_SYMBOL_GPL(vhost_enable_notify); -- 2.31.1 _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
