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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 03.07.14 at 16:53, <Ian.Campbell@xxxxxxxxxx> wrote:
> On Thu, 2014-07-03 at 15:50 +0100, Ian Campbell wrote:
>> What specifically should Arianna be looking for? THe PCI device class or
>> something else?
> 
> Qemu-trad seems to use:
>     if ( !gfx_passthru || real_device->pci_dev->device_class != 0x0300 )
>         return ret;
> 
> Is that sufficient?

I don't think so - I'd expect secondary cards to also be showing this
class/sub-class (but I have no system with two or more cards where
I could at least empirically check), i.e. that would only be sufficient
when there's no upstream bridge. PCI_BRIDGE_CTL_VGA (on
upstream bridges) and maybe (but unlikely)
PCI_COMMAND_VGA_PALETTE (on the device itself and perhaps also
upstream bridges) would seem to be the indicators. But I'm afraid
this really needs to be properly answered by a PCI expert.

Jan


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