Re: [virtio-comment] Re: [PATCH v2 0/2] transport-pci: Introduce legacy registers access using AQ

[Jason Wang <jasowang@redhat.com>]

å 2023/5/11 19:35, Michael S. Tsirkin åé:
> On Thu, May 11, 2023 at 03:20:52PM +0800, Jason Wang wrote:
> > On Thu, May 11, 2023 at 12:08âAM Parav Pandit <parav@nvidia.com> wrote:
> > > On 5/10/2023 12:22 AM, Jason Wang wrote:
> > > > On Wed, May 10, 2023 at 11:51âAM Jason Wang <jasowang@redhat.com> wrote:
> > > > Just to make sure we are at the same page.
> > > >
> > > > 1) if the hardware has configq and we need to make it work for current
> > > > virtio-pci driver, hypervisor needs to trap guest PCI access and
> > > > translate it to configq command. This means the hypervisor needs to
> > > > hide the configq from guests. In this case the configq needs a
> > > > dedicated DMA address which is what PASID can help.
> > > > 2) if the hardware can report the device states, unless we want to
> > > > migrate L2 guest, hypervisor should hide it from L1, so PASID is
> > > > required to isolate the DMA for guest traffic and device state.
> > > A configq negotiates + discovers new fields for the PCI PF, VF, SF/SIOV
> > > devices over PCIe or other transports.
> > > So no need to hide/mediate for hw based devices, like cvq and like data vqs.
> > As discussed, I may misunderstand the function of the configq. If it
> > works like cvq, then yes. We don't need PASID.
> >
> > But if we want to report device state via let's say migration q, it
> > requires PASID since it is used by the hypervisor.
> >
> > Thanks
> I don't exactly get this part. With SRIOV migration q normally would be
> part of the PF, accessing hypervisor memory.


Yes, I meant if we have a per VF adminq.

Thanks


> > > For vdpa kind of use case it can work like cvq mediation, which I
> > > believe is happening without PASID today.
> > >
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