Jason Wang
2021-Feb-04 03:06 UTC
[PATCH net] virtio-net: suppress bad irq warning for tx napi
On 2021/2/4 ??2:28, Willem de Bruijn wrote:> On Wed, Feb 3, 2021 at 12:33 AM Jason Wang <jasowang at redhat.com> wrote: >> >> On 2021/2/2 ??10:37, Willem de Bruijn wrote: >>> On Mon, Feb 1, 2021 at 10:09 PM Jason Wang <jasowang at redhat.com> wrote: >>>> On 2021/1/29 ??8:21, 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> >>>> Please use get_maintainer.pl to make sure Michael and me were cced. >>> Will do. Sorry about that. I suggested just the virtualization list, my bad. >>> >>>>> --- >>>>> 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); >>>> Do we need to force the ordering between steal set and napi enable? >>> The warning only occurs after one hundred spurious interrupts, so not >>> really. >> >> Ok, so it looks like a hint. Then I wonder how much value do we need to >> introduce helper like virtqueue_set_work_steal() that allows the caller >> to toggle. How about disable the check forever during virtqueue >> initialization? > Yes, that is even simpler. > > We still need the helper, as the internal variables of vring_virtqueue > are not accessible from virtio-net. An earlier patch added the > variable to virtqueue itself, but I think it belongs in > vring_virtqueue. And the helper is not a lot of code.It's better to do this before the allocating the irq. But it looks not easy unless we extend find_vqs(). Thanks>
Willem de Bruijn
2021-Feb-04 20:50 UTC
[PATCH net] virtio-net: suppress bad irq warning for tx napi
On Wed, Feb 3, 2021 at 10:06 PM Jason Wang <jasowang at redhat.com> wrote:> > > On 2021/2/4 ??2:28, Willem de Bruijn wrote: > > On Wed, Feb 3, 2021 at 12:33 AM Jason Wang <jasowang at redhat.com> wrote: > >> > >> On 2021/2/2 ??10:37, Willem de Bruijn wrote: > >>> On Mon, Feb 1, 2021 at 10:09 PM Jason Wang <jasowang at redhat.com> wrote: > >>>> On 2021/1/29 ??8:21, 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> > >>>> Please use get_maintainer.pl to make sure Michael and me were cced. > >>> Will do. Sorry about that. I suggested just the virtualization list, my bad. > >>> > >>>>> --- > >>>>> 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); > >>>> Do we need to force the ordering between steal set and napi enable? > >>> The warning only occurs after one hundred spurious interrupts, so not > >>> really. > >> > >> Ok, so it looks like a hint. Then I wonder how much value do we need to > >> introduce helper like virtqueue_set_work_steal() that allows the caller > >> to toggle. How about disable the check forever during virtqueue > >> initialization? > > Yes, that is even simpler. > > > > We still need the helper, as the internal variables of vring_virtqueue > > are not accessible from virtio-net. An earlier patch added the > > variable to virtqueue itself, but I think it belongs in > > vring_virtqueue. And the helper is not a lot of code. > > > It's better to do this before the allocating the irq. But it looks not > easy unless we extend find_vqs().Can you elaborate why that is better? At virtnet_open the interrupts are not firing either. I have no preference. Just curious, especially if it complicates the patch.