Re: [PATCH] virtio-vga: fix virtio-vga bar ordering

[Gerd Hoffmann]

On Wed, Apr 22, 2020 at 02:04:36AM -0400, Michael S. Tsirkin wrote:
> On Tue, Apr 21, 2020 at 11:48:53PM +0200, Anthoine Bourgeois wrote:
> > With virtio-vga, pci bar are reordered. Bar #2 is used for compatibility
> > with stdvga. By default, bar #2 is used by virtio modern io bar.
> > This bar is the last one introduce in the virtio pci bar layout and it's
> > crushed by the virtio-vga reordering. So virtio-vga and
> > modern-pio-notify are incompatible because virtio-vga failed to
> > initialize with this option.
> > 
> > This fix exchange the modern io bar with the modern memory bar,
> > replacing the msix bar that is never impacted anyway.
> > 
> > Signed-off-by: Anthoine Bourgeois <address@hidden>
> 
> Such changes generally need to be tied to machine version.

Given that modern-pio-notify is off by default and
virtio-vga,modern-pio-notify=on is broken I think we don't need to worry
about compatibility in this specific case (assuming the patch is updated
to not shuffle around the msix bar, see other reply).

cheers,
  Gerd