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Date:   Thu, 22 Sep 2022 05:16:03 -0400
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     Junbo <junbo4242@gmail.com>
Cc:     Jason Wang <jasowang@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        John Fastabend <john.fastabend@gmail.com>,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [PATCH] Do not name control queue for virtio-net
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On Sun, Sep 18, 2022 at 05:00:20PM +0800, Junbo wrote:
> hi?Michael
> 
> in virtio-net.c
> ? ? /* Parameters for control virtqueue, if any */
> ? ? if (vi->has_cvq) {
> ? ? ? ? callbacks[total_vqs - 1] = NULL;
> ? ? ? ? names[total_vqs - 1] = "control";
> ? ? }
> 
> I think the Author who write the code maybe want to name the control queue to
> 'virtioX-control',

That would be me I suspect ;)

> but it never worked, we can see the name still be
> 'virtioX-config' in /proc/interrupts,

Nope, what you see in /proc/interrupts are the interrupts, not the queue
name.

> for example?
> ?43: ? ? ? ? ?0 ? ? ? ? ?0 ? ? ? ? ?0 ? ? ? ? ?0 ? ? ? ? ?0 ? ? ? ? ?0 ? ? ? ?
> ?0 ? ? ? ? ?0 ? PCI-MSI-edge ? ? ?virtio0-config
> ?44: ? ? ? ? 64 ? ? ? ? ?0 ? ? ? ? ?0 ? ? ? ? ?0 ? ? ? ? ?0 ? ? ? ? ?0 ? ? ?
> 1845 ? ? ? ? ?0 ? PCI-MSI-edge ? ? ?virtio0-input.0
> ?45: ? ? ? ? ?1 ? ? ? ? ?0 ? ? ? ? ?0 ? ? ? ? ?0 ? ? ? ? ?0 ? ? ? ? ?0 ? ? ? ?
> ?0 ? ? ? ? ?0 ? PCI-MSI-edge ? ? ?virtio0-output.0
> 
> Because in function?vp_request_msix_vectors, it just allocate 'xxxx-config' to
> every virtio devices, even the virtio device do not need it.

Oh yes, we can fix that. The result will be this line disappearing for
devices without a config interrupt. Not for net though, that
generally uses a config interrupt for things like link
state detection.


> in /proc/
> interrupts, we can see that each virtio device's first interrupt always named
> 'virtioX-config'.
> 
> So I think it's better to not explicitly give the "control" here, it's
> useless...??


it's used for debugging.