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

["Zhu, Lingshan" <lingshan.zhu@intel.com>]

On 8/16/2023 10:11 AM, Jason Wang wrote:
> 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.
OK, I will clarify this in the resting queue section.

This reminds me I should add: When SUSPEND is set, the \field{device 
status} is still operational for
both the device and the driver. Because after SUSPEND, the driver may 
set DRIVER_OK and the device may
set NEEDS_RESET.

Thanks
> Thanks
>
>
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