Re: [Xen-devel] [PATCH v9 12/14] tools/libxl: read from config if passing through primary GPU

[Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>]

On Thu, 2014-07-03 at 11:30 +0100, Jan Beulich wrote:
> >>> On 02.07.14 at 21:00, <linux@xxxxxxxxxxxxxx> wrote:
> > Wednesday, July 2, 2014, 8:42:21 PM, you wrote:
> >> --- a/docs/man/xl.cfg.pod.5
> >> +++ b/docs/man/xl.cfg.pod.5
> >> @@ -601,6 +601,13 @@ More information about Xen gfx_passthru feature is 
> >> available
> >>  on the XenVGAPassthrough L<http://wiki.xen.org/wiki/XenVGAPassthrough>
> >>  wiki page.
> >>  
> >> +=item B<gfx_passthru_primary=BOOLEAN>
> >> +
> >> +If set to true, indicates that one of the GPUs passed through to the
> >> +domain is the primary one; therefore allows to the domain's stubdoman
> >> +access permissions for the VGA framebuffer. Note that this option
> >> +defaults to true.
> >> +
> > 
> > Wouldn't it make sense to make it a pci <BDF> instead of boolean, 
> > so that instead of: "one of the GPU's passed is the primary",
> > you could actually specify: "this *specific* GPU passed through i would 
> > like 
> > to be the primary" ?
> 
> No. You can't just make some card primary (with "primary" really
> meaning accessible via the legacy VGA interface). Within a host
> there's exactly one card that can be primary. If that card gets
> passed through, it can also be primary in the guest. Any other
> card, not having the legacy VGA ports routed through the
> corresponding circuitry, can't all of the sudden become the
> primary one in a guest.
> 
> Consequently this shouldn't be a config file setting, but something
> that gets worked out by looking at the PCI config spaces of the
> passed through card and eventual upstream bridges.

What specifically should Arianna be looking for? THe PCI device class or
something else?

Ian.


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