On Tue, Aug 16, 2022 at 04:48:11PM +0200, Halil Pasic wrote:
> On Fri, 12 Aug 2022 13:19:20 -0400
> "Michael S. Tsirkin" <[email protected]> wrote:
>
> > Signed-off-by: Michael S. Tsirkin <[email protected]>
> > ---
> > content.tex | 10 ++++++++++
> > 1 file changed, 10 insertions(+)
> >
> > diff --git a/content.tex b/content.tex
> > index 76b5a28..53be680 100644
> > --- a/content.tex
> > +++ b/content.tex
> > @@ -2668,6 +2668,16 @@ \subsubsection{Handling Device
> > Features}\label{sec:Virtio Transport Options / Vi
> > uses the CCW_CMD_WRITE_FEAT command, denoting a
> > \field{features}/\field{index}
> > combination.
> >
> > +\devicenormative{\paragraph}{Handling Device Features}{Virtio Transport
> > Options / Virtio over channel I/O / Device Initialization / Handling Device
> > Features}
> > +
> > +Device MUST NOT set bit VIRTIO_F_ADMIN_VQ (bit 41) in
> > +DeviceFeatures.
> > +
> > +\drivernormative{\paragraph}{Handling Device Features}{Virtio Transport
> > Options / Virtio over channel I/O / Device Initialization / Handling Device
> > Features}
> > +
> > +Driver MUST NOT set bit VIRTIO_F_ADMIN_VQ (bit 41) in
> > +DriverFeatures even if offered by the device.
> > +
>
> I'm not sure I understand the intention here. I believe what we try to
> accomplish here is the following. The Channel I/O transport *currently*
> does not support the VIRTIO_F_ADMIN_VQ feature. It is not like we want
> to state that the feature VIRTIO_F_ADMIN_VQ won't ever be supported by
> the Channel I/O transport. Or am I wrong?
>
> If my assumptions are right, then the old incarnation of the spec could
> contradict the new incarnation of the spec. Thus I would prefer something
> like.
Relaxing requirenents is always okay.
>
> """
> Currently the following features are not supported by the Channel I/O
> transport:
> * VIRTIO_F_ADMIN_VQ
> """
what I want to prevent is driver saying "oh device will not set ADMIN_VQ
so it's ok to acknowledge it if offered, it is never offered even
though it does not suport it".
because then it becomes impossible to know when actually a new driver
appears with actual support.
So, Maybe just add text
Note: future versions of this specification will allow setting ADMIN_VQ
for driver and device. Device MUST NOT assume driver does not
acknowledge ADMIN_VQ if offered.
And similarly for drivers:
Note: future versions of this specification will allow setting ADMIN_VQ
for driver and device. Drivers MUST NOT assume ADMIN_VQ if not offered.
>
> If we want, we can also state what needs to be done in general when
> features are unsupported by the transport. And yes, that normative
> material in my opinion.
>
> Regards,
> Halil
Are there other examples? I want to call out the list explicitly because
it is so easy to enable an extra feature by mistake.
> > \subsubsection{Device Configuration}\label{sec:Virtio Transport Options /
> > Virtio over channel I/O / Device Initialization / Device Configuration}
> >
> > The device's configuration space is located in host memory.
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