Re: [Qemu-devel] [v6][PATCH 05/10] xen, gfx passthrough: basic graphics passthrough support

[Chen, Tiejun]

On 2015/1/20 16:14, Gerd Hoffmann wrote:
> On Di, 2015-01-20 at 11:14 +0800, Chen, Tiejun wrote:
> > On 2015/1/19 19:45, Gerd Hoffmann wrote:
> > > On Mo, 2015-01-19 at 17:28 +0800, Tiejun Chen wrote:
> > > > +DEF("gfx_passthru", 0, QEMU_OPTION_gfx_passthru,
> > > > +    "-gfx_passthru   enable Intel IGD passthrough by XEN\n",
> > > > +    QEMU_ARCH_ALL)
> > > > +STEXI
> > > > address@hidden -gfx_passthru
> > > > address@hidden -gfx_passthru
> > > > +Enable Intel IGD passthrough by XEN
> > > > +ETEXI
> > >
> > > Make that a machine option, i.e. "-machine pc,igd-passthru=on"?
> >
> > Yeah but I think we need "-machine xenfv,igd-passthru=on" here.
>
> IIRC xen decided to stop using xenfv and use pc-$version instead (with
> $version being what was current at release time, 1.6 for xen 4.4 I
> think, to avoid surprises like the address space layout changes in more
> recent machine types).

To be more exact, 'xen_platform_pci' should determine this at this point,

        if (!libxl_defbool_val(b_info->u.hvm.xen_platform_pci)) {
            /* Switching here to the machine "pc" which does not add
             * the xen-platform device instead of the default "xenfv" 
machine.
             */
            machinearg = libxl__sprintf(gc, "pc,accel=xen");
        } else {
            machinearg = libxl__sprintf(gc, "xenfv");
        }

But you may remember, in our case we always set 'xen_platform_pci=0' 
since we need to release slot 2 for IGD. So finally we really go pc case.

Anyway this means something should be changed to pass such a new machine 
property in Xen side. And I'll send a patch to address this firstly, 
then go back here.

Thanks
Tiejun