From: "Michael S. Tsirkin" <mst@redhat.com>
To: Gerd Hoffmann <kraxel@redhat.com>
Cc: Anthoine Bourgeois <anthoine.bourgeois@gmail.com>, qemu-devel@nongnu.org
Subject: Re: [PATCH] virtio-vga: fix virtio-vga bar ordering
Date: Wed, 22 Apr 2020 10:25:31 -0400 [thread overview]
Message-ID: <20200422102504-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20200422104941.qp4lkblm7txlglm2@sirius.home.kraxel.org>
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.bourgeois@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.
next prev parent reply other threads:[~2020-04-22 14:26 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-21 21:48 [PATCH] virtio-vga: fix virtio-vga bar ordering Anthoine Bourgeois
2020-04-22 6:04 ` Michael S. Tsirkin
2020-04-22 10:49 ` Gerd Hoffmann
2020-04-22 14:25 ` Michael S. Tsirkin [this message]
2020-04-22 10:46 ` Gerd Hoffmann
2020-04-22 22:02 ` Anthoine Bourgeois
2020-04-23 11:30 ` Gerd Hoffmann
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