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 09:25:51 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Wei Wang <weiwan@...gle.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, netdev@...r.kernel.org
Subject: Re: [PATCH net v2 0/2] virtio-net: suppress bad irq warning for tx
 napi

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.


> 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