Re: [virtio-comment] [PATCH V3 RESEND 1/4] Introduce virito transport virtqueue

[Jason Wang <jasowang@redhat.com>]

On Tue, Aug 9, 2022 at 5:28 PM Zhu, Lingshan <lingshan.zhu@intel.com> wrote:
>
>
>
> On 8/9/2022 5:21 PM, Jason Wang wrote:
> > On Tue, Aug 9, 2022 at 5:19 PM Zhu, Lingshan <lingshan.zhu@intel.com> wrote:
> >>
> >>
> >> On 8/9/2022 5:12 PM, Michael S. Tsirkin wrote:
> >>> On Tue, Aug 09, 2022 at 04:36:43PM +0800, Zhu, Lingshan wrote:
> >>>>>> +
> >>>>>> +A device that offers feature bit VIRTIO_F_TRANSPT_VQ and a transport virtqueue is a management device.
> >>>>>> +It processes the commands through the transport virtqueue commands.
> >>>>> I think we need to be verbose here, e.g what did those transport
> >>>>> virtqueue commands do? What's the relationship between management
> >>>>> device and managed device?
> >>>> I will add an overview of the transport virtqueue commands here, and a
> >>>> description of the relationship in the "managed device" section.
> >>> Transport is fine but management of devices is clearly something
> >>> nvidia's patches do. So I think it's best to reuse the concept of device
> >>> groups for this, from Max's patchset. Let's not replicate that work at
> >>> least. I promised Max to help a bit with wording so I'll soon send a
> >>> revision of his patchset, the generic part about device group
> >>> from which you should be able to reuse.
> >> Of course, it is possible to add the device groups in this series for sure.
> >>
> >> What I don't understand is: what kind of commands against a device
> >> group? Destroy all?
> >> And normally a parent device only support one kind of devices, like a
> >> SRIOV capable
> >> virtio-net PF only supports virtio-net VFs on it, and maybe there will
> >> not be
> >> a device support both SIOV and SRIOV, it is complex in the HW
> >> implementation.
> > For having backward compatibility? (E.g for platforms that don't support SIOV)
> >
> > Thanks
> If not a device model like SIOV which does not have a dedicated physical
> transport layer,
> the question would be: Why do we need a side channel for a VF? This
> looks conflicts with
> VF provisioning and virtio-spec definitions. E.g, why allow changing MSI
> in the flight
> outside the guest control?

Just to clarify my points. I meant that vendors may choose to
implement both SRIOV and SIOV in the hardware. And I believe this is
what most vendor will do.

But it doesn't mean the control path needs to be shared.

Thanks

>
> Thanks,
> Zhu Lingshan
> >
> >> Thanks,
> >> Zhu Lingshan
> >>
>