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

Parav Pandit
2023-05-15T17:51:14Z

> From: Michael S. Tsirkin <mst@redhat.com>
> Sent: Monday, May 15, 2023 1:45 PM
>
> On Mon, May 15, 2023 at 03:49:44PM +0000, Parav Pandit wrote:
> > All legacy interface via AQ.
> > All modern interface access via PCI or its own transport between driver and
> device.
>
> I am wondering however about the hypervisor notifications. Generally these
> are the most problematic aspect here I feel. For example, how does it interact
> with VIRTIO_F_NOTIF_CONFIG_DATA? And generally, having both guest and
> host be allowed to access device's BAR seems problematic.
> Can we reserve a PF BAR region for these things or is that too expensive?

VIRTIO_F_NOTIF_CONFIG_DATA is not present for the legacy.
For modern device, guest driver will access the device own BAR directly with its own config_data anyway.
Should we reserve a region in the PF BAR for SF/SIOV device?, should device report which BAR/area to use for the given SF/SIOV device?
May be yes, those are different discussions with tradeoff to consider during SIOV discussions. It is not related to VFs.