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* [PATCH -next v2] virtio_net: Avoid loop in virtnet_poll
       [not found] <20200802003818-mutt-send-email-mst@kernel.org>
@ 2020-08-02  5:56 ` Mao Wenan
  2020-08-02  6:25   ` Michael S. Tsirkin
  2020-08-02  6:26   ` Michael S. Tsirkin
  0 siblings, 2 replies; 6+ messages in thread
From: Mao Wenan @ 2020-08-02  5:56 UTC (permalink / raw)
  To: mst, jasowang; +Cc: virtualization, linux-kernel, kernel-janitors, Mao Wenan

The loop may exist if vq->broken is true,
virtqueue_get_buf_ctx_packed or virtqueue_get_buf_ctx_split
will return NULL, so virtnet_poll will reschedule napi to
receive packet, it will lead cpu usage(si) to 100%.

call trace as below:
virtnet_poll
	virtnet_receive
		virtqueue_get_buf_ctx
			virtqueue_get_buf_ctx_packed
			virtqueue_get_buf_ctx_split
	virtqueue_napi_complete
		virtqueue_poll           //return true
		virtqueue_napi_schedule //it will reschedule napi

To fix this, return false if vq is broken in virtqueue_poll.

Signed-off-by: Mao Wenan <wenan.mao@linux.alibaba.com>
---
 v1->v2: fix it in virtqueue_poll suggested by Michael S. Tsirkin <mst@redhat.com>
 drivers/virtio/virtio_ring.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 58b96ba..4f7c73e 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1960,6 +1960,9 @@ bool virtqueue_poll(struct virtqueue *_vq, unsigned last_used_idx)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
 
+	if (unlikely(vq->broken))
+		return false;
+
 	virtio_mb(vq->weak_barriers);
 	return vq->packed_ring ? virtqueue_poll_packed(_vq, last_used_idx) :
 				 virtqueue_poll_split(_vq, last_used_idx);
-- 
1.8.3.1


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH -next v2] virtio_net: Avoid loop in virtnet_poll
  2020-08-02  5:56 ` [PATCH -next v2] virtio_net: Avoid loop in virtnet_poll Mao Wenan
@ 2020-08-02  6:25   ` Michael S. Tsirkin
  2020-08-02  6:26   ` Michael S. Tsirkin
  1 sibling, 0 replies; 6+ messages in thread
From: Michael S. Tsirkin @ 2020-08-02  6:25 UTC (permalink / raw)
  To: Mao Wenan; +Cc: jasowang, virtualization, linux-kernel, kernel-janitors

On Sun, Aug 02, 2020 at 01:56:33PM +0800, Mao Wenan wrote:
> The loop may exist if vq->broken is true,
> virtqueue_get_buf_ctx_packed or virtqueue_get_buf_ctx_split
> will return NULL, so virtnet_poll will reschedule napi to
> receive packet, it will lead cpu usage(si) to 100%.
> 
> call trace as below:
> virtnet_poll
> 	virtnet_receive
> 		virtqueue_get_buf_ctx
> 			virtqueue_get_buf_ctx_packed
> 			virtqueue_get_buf_ctx_split
> 	virtqueue_napi_complete
> 		virtqueue_poll           //return true
> 		virtqueue_napi_schedule //it will reschedule napi
> 
> To fix this, return false if vq is broken in virtqueue_poll.
> 
> Signed-off-by: Mao Wenan <wenan.mao@linux.alibaba.com>

Looks good:
Acked-by: Michael S. Tsirkin <mst@redhat.com>

> ---
>  v1->v2: fix it in virtqueue_poll suggested by Michael S. Tsirkin <mst@redhat.com>
>  drivers/virtio/virtio_ring.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 58b96ba..4f7c73e 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -1960,6 +1960,9 @@ bool virtqueue_poll(struct virtqueue *_vq, unsigned last_used_idx)
>  {
>  	struct vring_virtqueue *vq = to_vvq(_vq);
>  
> +	if (unlikely(vq->broken))
> +		return false;
> +
>  	virtio_mb(vq->weak_barriers);
>  	return vq->packed_ring ? virtqueue_poll_packed(_vq, last_used_idx) :
>  				 virtqueue_poll_split(_vq, last_used_idx);
> -- 
> 1.8.3.1


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH -next v2] virtio_net: Avoid loop in virtnet_poll
  2020-08-02  5:56 ` [PATCH -next v2] virtio_net: Avoid loop in virtnet_poll Mao Wenan
  2020-08-02  6:25   ` Michael S. Tsirkin
@ 2020-08-02  6:26   ` Michael S. Tsirkin
  2020-08-02  7:31     ` maowenan
  2020-08-02  7:44     ` [PATCH -next v3] virtio_ring: Avoid loop when vq is broken in virtqueue_poll Mao Wenan
  1 sibling, 2 replies; 6+ messages in thread
From: Michael S. Tsirkin @ 2020-08-02  6:26 UTC (permalink / raw)
  To: Mao Wenan; +Cc: jasowang, virtualization, linux-kernel, kernel-janitors


Just noticed the subject is wrong: this is no longer
a virtio_net patch.

On Sun, Aug 02, 2020 at 01:56:33PM +0800, Mao Wenan wrote:
> The loop may exist if vq->broken is true,
> virtqueue_get_buf_ctx_packed or virtqueue_get_buf_ctx_split
> will return NULL, so virtnet_poll will reschedule napi to
> receive packet, it will lead cpu usage(si) to 100%.
> 
> call trace as below:
> virtnet_poll
> 	virtnet_receive
> 		virtqueue_get_buf_ctx
> 			virtqueue_get_buf_ctx_packed
> 			virtqueue_get_buf_ctx_split
> 	virtqueue_napi_complete
> 		virtqueue_poll           //return true
> 		virtqueue_napi_schedule //it will reschedule napi
> 
> To fix this, return false if vq is broken in virtqueue_poll.
> 
> Signed-off-by: Mao Wenan <wenan.mao@linux.alibaba.com>
> ---
>  v1->v2: fix it in virtqueue_poll suggested by Michael S. Tsirkin <mst@redhat.com>
>  drivers/virtio/virtio_ring.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 58b96ba..4f7c73e 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -1960,6 +1960,9 @@ bool virtqueue_poll(struct virtqueue *_vq, unsigned last_used_idx)
>  {
>  	struct vring_virtqueue *vq = to_vvq(_vq);
>  
> +	if (unlikely(vq->broken))
> +		return false;
> +
>  	virtio_mb(vq->weak_barriers);
>  	return vq->packed_ring ? virtqueue_poll_packed(_vq, last_used_idx) :
>  				 virtqueue_poll_split(_vq, last_used_idx);
> -- 
> 1.8.3.1


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH -next v2] virtio_net: Avoid loop in virtnet_poll
  2020-08-02  6:26   ` Michael S. Tsirkin
@ 2020-08-02  7:31     ` maowenan
  2020-08-02  7:44     ` [PATCH -next v3] virtio_ring: Avoid loop when vq is broken in virtqueue_poll Mao Wenan
  1 sibling, 0 replies; 6+ messages in thread
From: maowenan @ 2020-08-02  7:31 UTC (permalink / raw)
  To: Michael S. Tsirkin
  Cc: jasowang, virtualization, linux-kernel, kernel-janitors



On 8/2/20 2:26 PM, Michael S. Tsirkin wrote:
> 
> Just noticed the subject is wrong: this is no longer
> a virtio_net patch.

thanks, I will change the subject and send v3.

^ permalink raw reply	[flat|nested] 6+ messages in thread

* [PATCH -next v3] virtio_ring: Avoid loop when vq is broken in virtqueue_poll
  2020-08-02  6:26   ` Michael S. Tsirkin
  2020-08-02  7:31     ` maowenan
@ 2020-08-02  7:44     ` Mao Wenan
  2020-08-04  2:42       ` Jason Wang
  1 sibling, 1 reply; 6+ messages in thread
From: Mao Wenan @ 2020-08-02  7:44 UTC (permalink / raw)
  To: mst, jasowang; +Cc: virtualization, linux-kernel, kernel-janitors, Mao Wenan

The loop may exist if vq->broken is true,
virtqueue_get_buf_ctx_packed or virtqueue_get_buf_ctx_split
will return NULL, so virtnet_poll will reschedule napi to
receive packet, it will lead cpu usage(si) to 100%.

call trace as below:
virtnet_poll
	virtnet_receive
		virtqueue_get_buf_ctx
			virtqueue_get_buf_ctx_packed
			virtqueue_get_buf_ctx_split
	virtqueue_napi_complete
		virtqueue_poll           //return true
		virtqueue_napi_schedule //it will reschedule napi

to fix this, return false if vq is broken in virtqueue_poll.

Signed-off-by: Mao Wenan <wenan.mao@linux.alibaba.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
---
 v2->v3: change subject, original is : "virtio_net: Avoid loop in virtnet_poll"
 v1->v2: fix it in virtqueue_poll suggested by Michael S. Tsirkin <mst@redhat.com>
 drivers/virtio/virtio_ring.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 58b96ba..4f7c73e 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1960,6 +1960,9 @@ bool virtqueue_poll(struct virtqueue *_vq, unsigned last_used_idx)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
 
+	if (unlikely(vq->broken))
+		return false;
+
 	virtio_mb(vq->weak_barriers);
 	return vq->packed_ring ? virtqueue_poll_packed(_vq, last_used_idx) :
 				 virtqueue_poll_split(_vq, last_used_idx);
-- 
1.8.3.1


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH -next v3] virtio_ring: Avoid loop when vq is broken in virtqueue_poll
  2020-08-02  7:44     ` [PATCH -next v3] virtio_ring: Avoid loop when vq is broken in virtqueue_poll Mao Wenan
@ 2020-08-04  2:42       ` Jason Wang
  0 siblings, 0 replies; 6+ messages in thread
From: Jason Wang @ 2020-08-04  2:42 UTC (permalink / raw)
  To: Mao Wenan, mst; +Cc: virtualization, linux-kernel, kernel-janitors


On 2020/8/2 下午3:44, Mao Wenan wrote:
> The loop may exist if vq->broken is true,
> virtqueue_get_buf_ctx_packed or virtqueue_get_buf_ctx_split
> will return NULL, so virtnet_poll will reschedule napi to
> receive packet, it will lead cpu usage(si) to 100%.
>
> call trace as below:
> virtnet_poll
> 	virtnet_receive
> 		virtqueue_get_buf_ctx
> 			virtqueue_get_buf_ctx_packed
> 			virtqueue_get_buf_ctx_split
> 	virtqueue_napi_complete
> 		virtqueue_poll           //return true
> 		virtqueue_napi_schedule //it will reschedule napi
>
> to fix this, return false if vq is broken in virtqueue_poll.
>
> Signed-off-by: Mao Wenan <wenan.mao@linux.alibaba.com>
> Acked-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>   v2->v3: change subject, original is : "virtio_net: Avoid loop in virtnet_poll"
>   v1->v2: fix it in virtqueue_poll suggested by Michael S. Tsirkin <mst@redhat.com>
>   drivers/virtio/virtio_ring.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 58b96ba..4f7c73e 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -1960,6 +1960,9 @@ bool virtqueue_poll(struct virtqueue *_vq, unsigned last_used_idx)
>   {
>   	struct vring_virtqueue *vq = to_vvq(_vq);
>   
> +	if (unlikely(vq->broken))
> +		return false;
> +
>   	virtio_mb(vq->weak_barriers);
>   	return vq->packed_ring ? virtqueue_poll_packed(_vq, last_used_idx) :
>   				 virtqueue_poll_split(_vq, last_used_idx);


Acked-by: Jason Wang <jasowang@redhat.com>



^ permalink raw reply	[flat|nested] 6+ messages in thread

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Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
     [not found] <20200802003818-mutt-send-email-mst@kernel.org>
2020-08-02  5:56 ` [PATCH -next v2] virtio_net: Avoid loop in virtnet_poll Mao Wenan
2020-08-02  6:25   ` Michael S. Tsirkin
2020-08-02  6:26   ` Michael S. Tsirkin
2020-08-02  7:31     ` maowenan
2020-08-02  7:44     ` [PATCH -next v3] virtio_ring: Avoid loop when vq is broken in virtqueue_poll Mao Wenan
2020-08-04  2:42       ` Jason Wang

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