Re: [virtio] [PATCH RFC v7 6/8] ccw: disallow ADMIN_VQ

[Halil Pasic <pasic@linux.ibm.com>]

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.

"""
Currently the following features are not supported by the Channel I/O
transport:
* VIRTIO_F_ADMIN_VQ
"""


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

>  \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.