Re: [RFC PATCH 4/5] virtqueue: constraints for virtqueue state

[Jason Wang <jasowang@redhat.com>]

On Tue, Aug 15, 2023 at 7:30âPM Zhu, Lingshan <lingshan.zhu@intel.com> wrote:
>
>
>
> On 8/15/2023 8:34 AM, Jason Wang wrote:
> > On Mon, Aug 14, 2023 at 7:29âPM Zhu Lingshan <lingshan.zhu@intel.com> wrote:
> >> This commit specifies the constraints of the virtqueue state,
> >> and the actions should be taken by the device when SUSPEND
> >> and DRIVER_OK is set
> >>
> >> Signed-off-by: Jason Wang <jasowang@redhat.com>
> >> Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
> >> ---
> >>   content.tex | 31 +++++++++++++++++++++++++++++++
> >>   1 file changed, 31 insertions(+)
> >>
> >> diff --git a/content.tex b/content.tex
> >> index 43bd5de..f6ac581 100644
> >> --- a/content.tex
> >> +++ b/content.tex
> >> @@ -587,6 +587,37 @@ \subsection{\field{Used State} Field}
> >>
> >>   See also \ref{sec:Packed Virtqueues / Driver and Device Ring Wrap Counters}.
> >>
> >> +\drivernormative{\subsection}{Virtqueue State}{Basic Facilities of a Virtio Device / Virtqueue State}
> >> +
> >> +If VIRTIO_F_QUEUE_STATE has been negotiated, the driver MUST set SUSPEND in \field{device status}
> >> +first before getting or setting Virtqueue State of any virtqueues.
> > I don't get why this is a must. It could be useful for debugging.
> To avoid race conditions with the device and make the device
> implementation easier

replied in another thread.

> >
> >> +
> >> +If VIRTIO_F_QUEUE_STATE has been negotiaged but VIRTIO_RING_F_PACKED not been negotiated,
> > typo
> yes
> >
> >> +the driver MUST NOT access \field{Used State} of any virtqueues, it should use the
> >> +used index in the used ring.
> >> +
> >> +\devicenormative{\subsection}{Virtqueue State}{Basic Facilities of a Virtio Device / Virtqueue State}
> >> +
> >> +If VIRTIO_F_QUEUE_STATE has been negotiated but SUSPEND is not set in \field{device status},
> >> +the device MUST ignore any accesses against Virtqueue State of any virtqueues.
> > Btw, do we need to clarify the behavior of ring reset after suspending?
> I think once suspended, the device should ignore resetting a queue

This needs to be clarified.

Thanks