Re: [Qemu-devel] [Xen-devel] [v2][PATCH 4/8] xen, gfx passthrough: reserve 00:02.0 for INTEL IGD

["Chen, Tiejun" <tiejun.chen@intel.com>]

> -----Original Message-----
> From: Fabio Fantoni [mailto:fabio.fantoni@m2r.biz]
> Sent: Monday, May 19, 2014 3:48 PM
> To: Gerd Hoffmann; Chen, Tiejun
> Cc: peter.maydell@linaro.org; xen-devel@lists.xensource.com;
> mst@redhat.com; Kay, Allen M; stefano.stabellini@eu.citrix.com;
> weidong.han@intel.com; Kelly.Zytaruk@amd.com;
> jean.guyader@eu.citrix.com; qemu-devel@nongnu.org; Zhang, Yang Z;
> anthony@codemonkey.ws; anthony.perard@citrix.com
> Subject: Re: [Xen-devel] [Qemu-devel] [v2][PATCH 4/8] xen, gfx passthrough:
> reserve 00:02.0 for INTEL IGD
> 
> Il 19/05/2014 08:44, Gerd Hoffmann ha scritto:
> >    Hi,
> >
> >> +    /*
> >> +     * Some video bioses and gfx drivers will assume the bdf of IGD is
> 00:02.0.
> >> +     * So user need to set it to 00:02.0 in Xen configure file explicitly,
> >> +     * otherwise IGD will fail to work.
> >> +     */
> >> +    pci_reserve_pci_devfn(b, PCI_DEVFN(2, 0));
> > That is asking for trouble.  Slot 2 is used by the qemu vga cards by
> > default, and for quite a while (before memory api was merged) it even
> > was impossible to change it.  libvirt still places the vga card at
> > slot
> > 2 for that reason -> boom.  I wouldn't be surprised if you find that
> > assumption in other management libs / apps too.
> >
> > Why do you need that patch in the first place?  It should be possible
> > to configure qemu to not occupy slot 2 if you need it that way.  Just
> > pass '-vga none' to qemu.  Which you probably want anyway if you
> > pass-through a vga to the guest.  And explicitly configure a slot (via
> > addr=
> > property) for all your pci devices.  Doing it only for the IGD works
> > too if you list the device before any other pci device on the qemu
> > command line.
> >
> > cheers,
> >    Gerd
> 
> I already added vga none support on libxl, useful also for this cases:
> http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=2e5738ff47b9d2e19480
> 24100f87b1a25fcf004a
> 
> This patch is already tested and working, for now I not tested and I can't test
> with intel gpu passthrough, someone can test it with intel gpu passthrough?
> 
> Thanks for any reply and sorry for my bad english.


But I think what we intend is to reserve a specific slot to work vga passthrough on IGD. 

Thanks
Tiejun