[v2] vhost: fix interrupt suppression for the split ring

  The VIRTIO_RING_F_EVENT_IDX feature of split ring might
be broken, as the value of signalled_used is invalid
after live migration, start up and virtio driver reload.
This patch fixes it by using signalled_used_valid.

In addition, this patch makes the VIRTIO_RING_F_EVENT_IDX
implementation of split ring match kernel backend to suppress
more interrupts.

Fixes: e37ff954405a ("vhost: support virtqueue interrupt/notification suppression")
Cc: stable@dpdk.org

Signed-off-by: Jiayu Hu <jiayu.hu@intel.com>
---
change in v2:
- fix virtio-net driver reload

 lib/librte_vhost/vhost.h      | 12 ++++++++----
 lib/librte_vhost/vhost_user.c |  2 ++
 2 files changed, 10 insertions(+), 4 deletions(-)
  

Test-by: Wang, Yinan <yinan.wang@intel.com>

Best Wishes,
Yinan

> -----Original Message-----
> From: Hu, Jiayu
> Sent: 2019年3月17日 14:39
> To: dev@dpdk.org
> Cc: Bie, Tiwei <tiwei.bie@intel.com>; maxime.coquelin@redhat.com; Wang,
> Yinan <yinan.wang@intel.com>; Hu, Jiayu <jiayu.hu@intel.com>;
> stable@dpdk.org
> Subject: [PATCH v2] vhost: fix interrupt suppression for the split ring
> 
> The VIRTIO_RING_F_EVENT_IDX feature of split ring might be broken, as the
> value of signalled_used is invalid after live migration, start up and virtio driver
> reload.
> This patch fixes it by using signalled_used_valid.
> 
> In addition, this patch makes the VIRTIO_RING_F_EVENT_IDX implementation
> of split ring match kernel backend to suppress more interrupts.
> 
> Fixes: e37ff954405a ("vhost: support virtqueue interrupt/notification
> suppression")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Jiayu Hu <jiayu.hu@intel.com>
> ---
> change in v2:
> - fix virtio-net driver reload
> 
>  lib/librte_vhost/vhost.h      | 12 ++++++++----
>  lib/librte_vhost/vhost_user.c |  2 ++
>  2 files changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h index
> f008ec4..e9138df 100644
> --- a/lib/librte_vhost/vhost.h
> +++ b/lib/librte_vhost/vhost.h
> @@ -633,16 +633,20 @@ vhost_vring_call_split(struct virtio_net *dev, struct
> vhost_virtqueue *vq)
>  	if (dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX)) {
>  		uint16_t old = vq->signalled_used;
>  		uint16_t new = vq->last_used_idx;
> +		bool signalled_used_valid = vq->signalled_used_valid;
> +
> +		vq->signalled_used = new;
> +		vq->signalled_used_valid = true;
> 
>  		VHOST_LOG_DEBUG(VHOST_DATA, "%s: used_event_idx=%d,
> old=%d, new=%d\n",
>  			__func__,
>  			vhost_used_event(vq),
>  			old, new);
> -		if (vhost_need_event(vhost_used_event(vq), new, old)
> -			&& (vq->callfd >= 0)) {
> -			vq->signalled_used = vq->last_used_idx;
> +
> +		if ((vhost_need_event(vhost_used_event(vq), new, old) &&
> +					(vq->callfd >= 0)) ||
> +				unlikely(!signalled_used_valid))
>  			eventfd_write(vq->callfd, (eventfd_t) 1);
> -		}
>  	} else {
>  		/* Kick the guest if necessary. */
>  		if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT) diff --git
> a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c index
> 36c0c67..01a8d80 100644
> --- a/lib/librte_vhost/vhost_user.c
> +++ b/lib/librte_vhost/vhost_user.c
> @@ -1298,6 +1298,8 @@ vhost_user_get_vring_base(struct virtio_net
> **pdev,
> 
>  	vq->callfd = VIRTIO_UNINITIALIZED_EVENTFD;
> 
> +	vq->signalled_used_valid = false;
> +
>  	if (dev->dequeue_zero_copy)
>  		free_zmbufs(vq);
>  	if (vq_is_packed(dev)) {
> --
> 2.7.4
  

On Sun, Mar 17, 2019 at 02:38:32PM +0800, Jiayu Hu wrote:
> The VIRTIO_RING_F_EVENT_IDX feature of split ring might
> be broken, as the value of signalled_used is invalid
> after live migration, start up and virtio driver reload.
> This patch fixes it by using signalled_used_valid.
> 
> In addition, this patch makes the VIRTIO_RING_F_EVENT_IDX
> implementation of split ring match kernel backend to suppress
> more interrupts.
> 
> Fixes: e37ff954405a ("vhost: support virtqueue interrupt/notification suppression")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Jiayu Hu <jiayu.hu@intel.com>
> ---
> change in v2:
> - fix virtio-net driver reload
> 
>  lib/librte_vhost/vhost.h      | 12 ++++++++----
>  lib/librte_vhost/vhost_user.c |  2 ++
>  2 files changed, 10 insertions(+), 4 deletions(-)

Reviewed-by: Tiwei Bie <tiwei.bie@intel.com>
  

On 3/17/19 7:38 AM, Jiayu Hu wrote:
> The VIRTIO_RING_F_EVENT_IDX feature of split ring might
> be broken, as the value of signalled_used is invalid
> after live migration, start up and virtio driver reload.
> This patch fixes it by using signalled_used_valid.
> 
> In addition, this patch makes the VIRTIO_RING_F_EVENT_IDX
> implementation of split ring match kernel backend to suppress
> more interrupts.
> 
> Fixes: e37ff954405a ("vhost: support virtqueue interrupt/notification suppression")
> Cc:stable@dpdk.org
> 
> Signed-off-by: Jiayu Hu<jiayu.hu@intel.com>
> ---
> change in v2:
> - fix virtio-net driver reload
> 
>   lib/librte_vhost/vhost.h      | 12 ++++++++----
>   lib/librte_vhost/vhost_user.c |  2 ++
>   2 files changed, 10 insertions(+), 4 deletions(-)


Applied to dpdk-next-virtio/master branch.

Thanks,
Maxime