[virtio-dev] Re: [virtio-comment] Re: [PATCH 09/11] transport-pci: Describe PCI MMR dev config registers

Michael S. Tsirkin
2023-04-16T20:44:36Z

On Sun, Apr 16, 2023 at 01:41:55PM +0000, Parav Pandit wrote:
> > From: virtio-comment@lists.oasis-open.org <virtio-comment@lists.oasis-
> > open.org> On Behalf Of Michael S. Tsirkin
> > Sent: Friday, April 14, 2023 2:57 AM
>
> > Do you refer to the trick Jason proposed where BAR0 is memory but otherwise
> > matches legacy BAR0 exactly? Is this your preferred solution at this point then?
>
> We look at it again.
> Above solution can work reliably only for a very small number of PF and that too with very special hardware circuitry due to the reset flow.
>
> Therefore, for virtualization below interface is preferred.
> a. For transitional device legacy configuration register transport over AQ,

I don't get what this has to do with transitional ...

> Notification to utilize transitional device notification area of the BAR.

The vq transport does something like this, no?

> b. Non legacy interface of transitional and non-transitional PCI device to access direct PCI device without mediation.

So VF can either be accessed through AQ of PF, or through direct
mapping?

--
MST