Re: [RFC PATCH 4/4] virtio-net: sleep instead of busy waiting for cvq command

[Jason Wang]

On Fri, Dec 23, 2022 at 3:39 PM Alvaro Karsz <alvaro.karsz@xxxxxxxxxxxxx> wrote:
>
> > This needs to be proposed to the virtio spec first. And actually we
> > need more than this:
> >
> > 1) we still need a way to deal with the device without this feature
> > 2) driver can't depend solely on what is advertised by the device (e.g
> > device can choose to advertise a very long timeout)
>
> I think that I wasn't clear, sorry.
> I'm not talking about a new virtio feature, I'm talking about a situation when:
> * virtio_net issues a control command.
> * the device gets the command, but somehow, completes the command
> after timeout.
> * virtio_net assumes that the command failed (timeout), and issues a
> different control command.
> * virtio_net will then call virtqueue_wait_for_used, and will
> immediately get the previous response (If I'm not wrong).
>
> So, this is not a new feature that I'm proposing, just a situation
> that may occur due to cvq timeouts.
>
> Anyhow, your solution calling BAD_RING if we reach a timeout should
> prevent this situation.

Right, that is the goal.

Thanks

>
> Thanks
>