Re: [Qemu-devel] [Xen-devel] [iGVT-g] [vfio-users] [PATCH v3 00/11] igd passthrough chipset tweaks

[Tian, Kevin]

> From: Kay, Allen M
> Sent: Tuesday, February 02, 2016 8:04 AM
> >
> > David notes in the latter commit above:
> >
> > "We should be able to successfully assign graphics devices to guests too, as
> > long as the initial handling of stolen memory is reconfigured 
> > appropriately."
> >
> > What code is supposed to be doing that reconfiguration when a device is
> > assigned?  Clearly we don't have it yet, making assignment of these devices
> > very unsafe.  It seems like vfio or IOMMU code  in the kernel needs device
> > specific code to clear these settings to make it safe for userspace, then
> > perhaps VM BIOS support to reallocate.  Is there any consistency across IGD
> > revisions for doing this?  Is there a spec?
> > Thanks,

I don't think stolen memory should be handled explicitly. If yes, it should be
listed as a RMRR region so general RMRR setup will cover it. But as Allen
pointed out, the whole RMRR becomes unnecessary if we target only secondary
device for IGD.

Thanks
Kevin