* Re: [PATCH -next v2] virtio_net: Avoid loop in virtnet_poll
[not found] ` <1596347793-55894-1-git-send-email-wenan.mao@linux.alibaba.com>
@ 2020-08-02 6:25 ` Michael S. Tsirkin
2020-08-02 6:26 ` Michael S. Tsirkin
1 sibling, 0 replies; 3+ messages in thread
From: Michael S. Tsirkin @ 2020-08-02 6:25 UTC (permalink / raw)
To: Mao Wenan; +Cc: kernel-janitors, linux-kernel, virtualization
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
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH -next v2] virtio_net: Avoid loop in virtnet_poll
[not found] ` <1596347793-55894-1-git-send-email-wenan.mao@linux.alibaba.com>
2020-08-02 6:25 ` [PATCH -next v2] virtio_net: Avoid loop in virtnet_poll Michael S. Tsirkin
@ 2020-08-02 6:26 ` Michael S. Tsirkin
[not found] ` <1596354249-96204-1-git-send-email-wenan.mao@linux.alibaba.com>
1 sibling, 1 reply; 3+ messages in thread
From: Michael S. Tsirkin @ 2020-08-02 6:26 UTC (permalink / raw)
To: Mao Wenan; +Cc: kernel-janitors, linux-kernel, virtualization
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
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH -next v3] virtio_ring: Avoid loop when vq is broken in virtqueue_poll
[not found] ` <1596354249-96204-1-git-send-email-wenan.mao@linux.alibaba.com>
@ 2020-08-04 2:42 ` Jason Wang
0 siblings, 0 replies; 3+ messages in thread
From: Jason Wang @ 2020-08-04 2:42 UTC (permalink / raw)
To: Mao Wenan, mst; +Cc: kernel-janitors, linux-kernel, virtualization
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>
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[not found] ` <1596347793-55894-1-git-send-email-wenan.mao@linux.alibaba.com>
2020-08-02 6:25 ` [PATCH -next v2] virtio_net: Avoid loop in virtnet_poll Michael S. Tsirkin
2020-08-02 6:26 ` Michael S. Tsirkin
[not found] ` <1596354249-96204-1-git-send-email-wenan.mao@linux.alibaba.com>
2020-08-04 2:42 ` [PATCH -next v3] virtio_ring: Avoid loop when vq is broken in virtqueue_poll Jason Wang
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