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

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Message-Id: <20210220014436.3556492-1-weiwan@google.com>
Date:   Fri, 19 Feb 2021 17:44:34 -0800
From:   Wei Wang <weiwan@...gle.com>
To:     "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Willem de Bruijn <willemb@...gle.com>,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: [PATCH net v2 0/2] virtio-net: suppress bad irq warning for tx napi

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.

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