[virtio-comment] Re: proposal: use admin command (and aq) of the device to query config space

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

On Wed, Aug 02, 2023 at 10:00:09AM +0000, Parav Pandit wrote:
> 
> 
> > From: Zhu, Lingshan <lingshan.zhu@intel.com>
> > Sent: Wednesday, August 2, 2023 3:11 PM
> 
> > > Get and set both should be inband for PF, VF, SIOV.
> > > I don’t see any need to diverge and create any weird combinations differently
> > for 3 different device types.
> > I am not sure, when passthrough a device to a guest, the guest driver ownes the
> > config space of the device, if we allow changes against the config space through
> > admin vq from host, it looks like a risk.
> 
> I said the opposite above, get and set is INBAND from guest driver to device for PF, VF and SIOV through its own delegated resource.
> There is no AQ mediation from host.
> Hence, there is no risk.

I think there are different requirements from different people.  For
example, consider compatibility. I know it looks like super important
right now, and we should make it possible, but it's just like with
legacy interface - looked very far away when we introduced
non-transitional, to the point where an option in linux to disable
legacy talks about "flying cars", but the flying cars are nowhere to be
seen and, while we are not where everyone can just drop pre-1.0 bits, a
bunch of people are using e.g. vdpa without any legacy, express devices
in qemu also disabled legacy, and so on.


-- 
MST


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