Re: [PATCH v12 05/10] pci: add admin vq registers to virtio over pci

[Max Gurtovoy <mgurtovoy@nvidia.com>]

On 27/04/2023 1:11, Parav Pandit wrote:
> > From: Max Gurtovoy <mgurtovoy@nvidia.com>
> > Sent: Wednesday, April 26, 2023 5:12 PM
> >
> > On 25/04/2023 1:14, Parav Pandit wrote:
> > > On 4/24/2023 6:06 PM, Max Gurtovoy wrote:
> > >
> > > > > +If VIRTIO_F_ADMIN_VQ has been negotiated, and if the driver
> > > > > +configures any administration virtqueues, the driver MUST configure
> > > > > +the administration virtqueues using the index in the range
> > > > > +\field{admin_queue_index} to \field{admin_queue_index} +
> > > > > +\field{admin_queue_num} - 1 inclusive.
> > > > > +The driver MAY configure less administration virtqueues than
> > > > > +supported by the device.
> > > >
> > > > we need to say something about other virtq's indexes.
> > > > For example, if aq index = 0 then for the vblk device the request
> > > > queues would start from index = 1.
> > > >
> > > > can we address this ?
> > >
> > > It may slightly complicate the device implementation when device
> > > dynamically changes the VQ indices based on the negotiation of the
> > > feature bit.
> > > Also the drivers with and without need a different VQ index handling.
> > >
> > > I am thinking that aq index should not overlap with the vq index in
> > > range exposed by num_queues field.
> > >
> > > This also aligns to the exclusion of aq count from num_queues field.
> >
> > The namespace of the aq and other vq index is the same.
> > And the configuration is done using the same queue_select and other registers.
> > Thus, we need to address the above comment otherwise all the device
> > virtqueues chapters are wrong.
>
> Michael has added below line in this patch in num_queues description so it covers the exclusion part.
>
> +        This excludes administration virtqueues if any are supported.

This is not related to what I was talking about.

For example if vnet device:

0 receiveq1
1 transmitq1
...
2(N-1) receiveqN
2(N-1)+1 transmitqN
2N controlq
N=1 if neither VIRTIO_NET_F_MQ nor VIRTIO_NET_F_RSS are negotiated, 
otherwise N is set by max_-
virtqueue_pairs.
controlq only exists if VIRTIO_NET_F_CTRL_VQ set

and in vfs device:

0 hiprio
1...n request queues

So if one device will expose adminq that will be with index 0 the above 
is wrong description.

Agree that this should be addressed ?