virtio — archive

[Michael S. Tsirkin <mst@redhat.com>]

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" <mst@redhat.com> wrote: > > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > > --- > > 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.