netdev - Re: [PATCH net v2 0/2] virtio-net: suppress bad irq warning for tx napi

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Date:   Tue, 23 Feb 2021 09:37:45 -0800
From:   Wei Wang <weiwan@...gle.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Jason Wang <jasowang@...hat.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        virtualization@...ts.linux-foundation.org,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH net v2 0/2] virtio-net: suppress bad irq warning for tx napi

On Tue, Feb 23, 2021 at 6:26 AM Michael S. Tsirkin <mst@...hat.com> wrote:
>
> On Fri, Feb 19, 2021 at 05:44:34PM -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 series contains 2 patches. The first one adds a new param to
> > struct vring_virtqueue to control if we want to suppress the bad irq
> > warning. And the second patch in virtio-net sets it for tx virtqueues if
> > napi-tx is enabled.
>
> I'm going to be busy until March, I think there should be a better
> way to fix this though. Will think about it and respond in about a week.
>
OK. Thanks.

>
> > Wei Wang (2):
> >   virtio: add a new parameter in struct virtqueue
> >   virtio-net: suppress bad irq warning for tx napi
> >
> >  drivers/net/virtio_net.c     | 19 ++++++++++++++-----
> >  drivers/virtio/virtio_ring.c | 16 ++++++++++++++++
> >  include/linux/virtio.h       |  2 ++
> >  3 files changed, 32 insertions(+), 5 deletions(-)
> >
> > --
> > 2.30.0.617.g56c4b15f3c-goog
>