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

Parav Pandit
2023-05-10T16:08:08Z

On 5/10/2023 12:22 AM, Jason Wang wrote:
> On Wed, May 10, 2023 at 11:51 AM 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.

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