* 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 _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization ^ 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 _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization ^ permalink raw reply [flat|nested] 3+ messages in thread
[parent not found: <1596354249-96204-1-git-send-email-wenan.mao@linux.alibaba.com>]
* 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> _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization ^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-08-02 6:25 ` [PATCH -next v2] virtio_net: Avoid loop in virtnet_poll Michael S. Tsirkin
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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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