Re: [virtio-comment] Re: [virtio-dev] Re: [PATCH v3 0/3] transport-pci: Introduce legacy registers access using AQ

[Jason Wang <jasowang@redhat.com>]

On Fri, Jun 9, 2023 at 10:58âAM Parav Pandit <parav@nvidia.com> wrote:
>
>
> > From: virtio-comment@lists.oasis-open.org <virtio-comment@lists.oasis-
> > open.org> On Behalf Of Jason Wang
> > Sent: Thursday, June 8, 2023 10:57 PM
>
> > > > In order to converge the discussion, maybe you can explain which one
> > > > of your 3 use cases and why can't work with _F_LEGACY_HEADER +
> > _F_LEGACY_MAC.
> > > Hypervisor does not involve in feature negotiation and device life cycle phase
> > so it cannot negotiate it.
> >
> > With  _F_LEGACY_HEADER + _F_LEGACY_MAC, hypervisor doesn't need to be
> > involved in the feature negotiation for modern devices as well.
> >
> Guest does not have this feature negotiation driver.
> Hypervisor is not involved.
> So, who negotiates?

When legacy drivers are doing feature negotiation, the hypervisor must
trap and negotiate those two features.
When modern drivers are doing the feature negotiation, the hypervisor
is not involved at all. So modern drivers can choose to negotiate (e.g
try to mediate legacy for L2) or not.

Thanks