Re: [virtio-dev] Re: [PATCH V5 2/2] virtio-gpio: Add support for interrupts

[Arnd Bergmann <arnd@kernel.org>]

On Tue, Jul 20, 2021 at 9:11 AM Viresh Kumar <viresh.kumar@linaro.org> wrote:
>
> On 20-07-21, 09:01, Arnd Bergmann wrote:
> > That's what I was hoping for, I'm just not sure if this is required
> > by the virtio spec or just the usual implementation of the device
> > side. Have you found a section in the spec that guarantees that
> > the virtqueue_kick() serves as a sufficient barrier that the driver
> > can rely on the information having arrived?
>
> This is what the spec say about it:
>
> https://docs.oasis-open.org/virtio/virtio/v1.1/csprd01/virtio-v1.1-csprd01.html#x1-9000023

I don't see it spell out whether this acts as a barrier or not. As far
as I can tell, the notification may be deferred, e.g. if the host is
multi-threaded and virtqueue_kick() needs to send an IPI to another
processor to look at the data.

       Arnd