[Intel-gfx] VGA arbiter support for Intel HD?

[Friedrich Oslage]

Hi,

several months ago Alex Williamson added a patch to the linux kernel to
enable VGA arbiter support for the IGD of Intel Core CPUs [1]. But just
a month after that the patch was reverted [2].

With these patches I am able to use VFIO and Qemu to passthrough a GTX
770 while using the Intel HD of a i7 4771 on the host for X.Org/XFCE.

Using the stock 3.14 kernel, without these patches, it doesn't work.
I believe the Nvidia card doesn't get initialized correctly...the
screen stays black and the guest OS is unreachable via network.


What is required to get these patches back into the mainline kernel? I
can not reproduce the issues described in the revert commit log,
perhaps we just need more testing?

Regards,
Friedrich

[1]
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=81b5c7bc8de3e6f63419139c2fc91bf81dea8a7d
[2]
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ebff5fa9d545574324095d9c6a3cb80c9157abc5