Michael S. Tsirkin
2021-Feb-02 23:11 UTC
[PATCH net] virtio-net: suppress bad irq warning for tx napi
On Thu, Jan 28, 2021 at 04:21:36PM -0800, Wei Wang wrote:> With the implementation of napi-tx in virtio driver, we clean tx > descriptors from rx napi handler, for the purpose of reducing tx > complete interrupts. But this could introduce a race where tx complete > interrupt has been raised, but the handler found there is no work to do > because we have done the work in the previous rx interrupt handler. > This could lead to the following warning msg: > [ 3588.010778] irq 38: nobody cared (try booting with the > "irqpoll" option) > [ 3588.017938] CPU: 4 PID: 0 Comm: swapper/4 Not tainted > 5.3.0-19-generic #20~18.04.2-Ubuntu > [ 3588.017940] Call Trace: > [ 3588.017942] <IRQ> > [ 3588.017951] dump_stack+0x63/0x85 > [ 3588.017953] __report_bad_irq+0x35/0xc0 > [ 3588.017955] note_interrupt+0x24b/0x2a0 > [ 3588.017956] handle_irq_event_percpu+0x54/0x80 > [ 3588.017957] handle_irq_event+0x3b/0x60 > [ 3588.017958] handle_edge_irq+0x83/0x1a0 > [ 3588.017961] handle_irq+0x20/0x30 > [ 3588.017964] do_IRQ+0x50/0xe0 > [ 3588.017966] common_interrupt+0xf/0xf > [ 3588.017966] </IRQ> > [ 3588.017989] handlers: > [ 3588.020374] [<000000001b9f1da8>] vring_interrupt > [ 3588.025099] Disabling IRQ #38 > > This patch adds a new param to struct vring_virtqueue, and we set it for > tx virtqueues if napi-tx is enabled, to suppress the warning in such > case. > > Fixes: 7b0411ef4aa6 ("virtio-net: clean tx descriptors from rx napi") > Reported-by: Rick Jones <jonesrick at google.com> > Signed-off-by: Wei Wang <weiwan at google.com> > Signed-off-by: Willem de Bruijn <willemb at google.com>This description does not make sense to me. irq X: nobody cared only triggers after an interrupt is unhandled repeatedly. So something causes a storm of useless tx interrupts here. Let's find out what it was please. What you are doing is just preventing linux from complaining.> --- > drivers/net/virtio_net.c | 19 ++++++++++++++----- > drivers/virtio/virtio_ring.c | 16 ++++++++++++++++ > include/linux/virtio.h | 2 ++ > 3 files changed, 32 insertions(+), 5 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 508408fbe78f..e9a3f30864e8 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -1303,13 +1303,22 @@ static void virtnet_napi_tx_enable(struct virtnet_info *vi, > return; > } > > + /* With napi_tx enabled, free_old_xmit_skbs() could be called from > + * rx napi handler. Set work_steal to suppress bad irq warning for > + * IRQ_NONE case from tx complete interrupt handler. > + */ > + virtqueue_set_work_steal(vq, true); > + > return virtnet_napi_enable(vq, napi); > } > > -static void virtnet_napi_tx_disable(struct napi_struct *napi) > +static void virtnet_napi_tx_disable(struct virtqueue *vq, > + struct napi_struct *napi) > { > - if (napi->weight) > + if (napi->weight) { > napi_disable(napi); > + virtqueue_set_work_steal(vq, false); > + } > } > > static void refill_work(struct work_struct *work) > @@ -1835,7 +1844,7 @@ static int virtnet_close(struct net_device *dev) > for (i = 0; i < vi->max_queue_pairs; i++) { > xdp_rxq_info_unreg(&vi->rq[i].xdp_rxq); > napi_disable(&vi->rq[i].napi); > - virtnet_napi_tx_disable(&vi->sq[i].napi); > + virtnet_napi_tx_disable(vi->sq[i].vq, &vi->sq[i].napi); > } > > return 0; > @@ -2315,7 +2324,7 @@ static void virtnet_freeze_down(struct virtio_device *vdev) > if (netif_running(vi->dev)) { > for (i = 0; i < vi->max_queue_pairs; i++) { > napi_disable(&vi->rq[i].napi); > - virtnet_napi_tx_disable(&vi->sq[i].napi); > + virtnet_napi_tx_disable(vi->sq[i].vq, &vi->sq[i].napi); > } > } > } > @@ -2440,7 +2449,7 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog, > if (netif_running(dev)) { > for (i = 0; i < vi->max_queue_pairs; i++) { > napi_disable(&vi->rq[i].napi); > - virtnet_napi_tx_disable(&vi->sq[i].napi); > + virtnet_napi_tx_disable(vi->sq[i].vq, &vi->sq[i].napi); > } > } > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index 71e16b53e9c1..f7c5d697c302 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -105,6 +105,9 @@ struct vring_virtqueue { > /* Host publishes avail event idx */ > bool event; > > + /* Tx side napi work could be done from rx side. */ > + bool work_steal; > + > /* Head of free buffer list. */ > unsigned int free_head; > /* Number we've added since last sync. */ > @@ -1604,6 +1607,7 @@ static struct virtqueue *vring_create_virtqueue_packed( > vq->notify = notify; > vq->weak_barriers = weak_barriers; > vq->broken = false; > + vq->work_steal = false; > vq->last_used_idx = 0; > vq->num_added = 0; > vq->packed_ring = true; > @@ -2038,6 +2042,9 @@ irqreturn_t vring_interrupt(int irq, void *_vq) > > if (!more_used(vq)) { > pr_debug("virtqueue interrupt with no work for %p\n", vq); > + if (vq->work_steal) > + return IRQ_HANDLED; > + > return IRQ_NONE; > } > > @@ -2082,6 +2089,7 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index, > vq->notify = notify; > vq->weak_barriers = weak_barriers; > vq->broken = false; > + vq->work_steal = false; > vq->last_used_idx = 0; > vq->num_added = 0; > vq->use_dma_api = vring_use_dma_api(vdev); > @@ -2266,6 +2274,14 @@ bool virtqueue_is_broken(struct virtqueue *_vq) > } > EXPORT_SYMBOL_GPL(virtqueue_is_broken); > > +void virtqueue_set_work_steal(struct virtqueue *_vq, bool val) > +{ > + struct vring_virtqueue *vq = to_vvq(_vq); > + > + vq->work_steal = val; > +} > +EXPORT_SYMBOL_GPL(virtqueue_set_work_steal); > + > /* > * This should prevent the device from being used, allowing drivers to > * recover. You may need to grab appropriate locks to flush. > diff --git a/include/linux/virtio.h b/include/linux/virtio.h > index 55ea329fe72a..091c30f21ff9 100644 > --- a/include/linux/virtio.h > +++ b/include/linux/virtio.h > @@ -84,6 +84,8 @@ unsigned int virtqueue_get_vring_size(struct virtqueue *vq); > > bool virtqueue_is_broken(struct virtqueue *vq); > > +void virtqueue_set_work_steal(struct virtqueue *vq, bool val); > + > const struct vring *virtqueue_get_vring(struct virtqueue *vq); > dma_addr_t virtqueue_get_desc_addr(struct virtqueue *vq); > dma_addr_t virtqueue_get_avail_addr(struct virtqueue *vq); > -- > 2.30.0.365.g02bc693789-goog >