[virtio-dev] RE: [virtio-comment] [PATCH 5/5] virtio-pci: implement VIRTIO_F_QUEUE_STATE

Parav Pandit
2023-09-19T07:33:21Z

> From: Jason Wang <jasowang@redhat.com>
> Sent: Tuesday, September 19, 2023 10:04 AM
>
> On Sun, Sep 17, 2023 at 1:25 PM Parav Pandit <parav@nvidia.com> wrote:
> >
> >
> > > From: Jason Wang <jasowang@redhat.com>
> > > Sent: Thursday, September 14, 2023 8:41 AM
> > >
> > > On Wed, Sep 13, 2023 at 12:37 PM Parav Pandit <parav@nvidia.com>
> wrote:
> > > >
> > > >
> > > >
> > > > > From: Zhu, Lingshan <lingshan.zhu@intel.com>
> > > > > Sent: Wednesday, September 13, 2023 9:51 AM
> > > >
> > > > > we plan to implement a self-contain solution
> > > > Make sure that works with device reset and FLR.
> > >
> > > We don't need to do that. It's out of the spec.
> > >
> > It is not. For the PCI member device, it needs to work reliably.
>
> We never mentioned FLR in the PCI transport layer before and vendors have
> produced tons of hardware PCI devices for several years.
It is not mentioned like many other PCI things because its native.
What I was saying is that if you are claiming that suspend, resume etc all are some basic facilities that can work with passthrough also, please show how it works with FLR in place.

>
> If it's important, please describe it in detail in your series but it doesn't.
>
It is mentioned. Please review there.

> > Not doing means it relies on the trap+emulation, hence it just cannot
> complete.
> > And it is ok to me.
> > I just wont claim that trap+emulation is _complete_ method.
> >
> > > > And if not, explain that it is for mediation mode related tricks.
> > >
> > > It's not the tricks and again, it's not mediation but trap and
> > > emulation. It's the fundamental methodology used in virtualization, so does
> the virtio spec.
> >
> > Not the virto spec of 2023 and more for new features.
> > The base for virtio spec 1.x was 0.9.5, but not the QEMU or other mediation
> based software AFAIK.
>
> Are you saying those new features will not be suitable for software devices? If
> yes, please explain why.
>
> Or are you saying the virtio spec is not capable for hardware devices?

No, you were hinting that trap+emulation is the fundamental technology of virtualization and virtio spec.

And I replied that for virtio spec 1.x only base line was spec 0.9.5, trap+emulation was not the base line when 1.x spec is drafted.

Virtio spec with few caveats is capable of hw and new sw, and it needs to continue to build new features that can work without trap+emulation mode.