On Wed, Apr 22, 2020 at 12:49:41PM +0200, Gerd Hoffmann wrote: > 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 <anthoine.bourge...@gmail.com> > > > > 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
OK, just worth documenting that this will break cross-version migration if modern-pio-notify is enabled.
