[libvirt] [PATCH] Fix explicit usage of default video PCI slots

[Daniel P. Berrange]

On Fri, Dec 20, 2013 at 10:17:22AM +0200, Laine Stump wrote:
> On 12/19/2013 07:41 PM, Ján Tomko wrote:
> > On 12/19/2013 06:18 PM, Jiri Denemark wrote:
> >> On Thu, Dec 19, 2013 at 17:43:33 +0100, Jano Tomko wrote:
> >>> Don't set the PCI address of primary video to the default
> >>> if it's already occupied by another device.
> >>>
> >>> Without this, a primary video card that doesn't have an
> >>> address gets the default one on the 1st pass of PCI address
> >>> allocation, even if it's occupied. This address gets picked
> >>> up by the second pass, and a conflict occurs:
> >>>
> >>> XML error: Attempted double use of PCI slot 0000:00:02.0
> >>> (may need "multifunction='on'" for device on function 0)
> >>>
> >>> Also fix the test that was supposed to catch this.
> >> And does it actually work after this patch? IIRC, the primary video card
> >> is forced to be at 0000:00:02.0 by QEMU. That is, if this address is
> >> occupied by another device, there should be no way to add a video card.
> >>
> > It works without this patch too, if you explicitly specify the PCI address of
> > the video card (and you have QEMU >= 1.6, because that's when we use -device
> > instead of -vga - (the QEMU_CAPS_DEVICE_VIDEO_PRIMARY capability)).
> 
> Isn't there also something about multi-display support that requires the
> primary video to be at a particular address?

FWIW, the only reason why I had hardcoded display originally was because
we were forced to use -vga instead of -device, and so could't control the
PCI port.

Daniel
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