Intel GPU with KMS locks up when visualization enabled

[Konstantin Belousov]

On Sun, Jul 15, 2012 at 04:09:18PM -0700, Kevin Oberman wrote:
> I don't have much information on this, but I wanted to enable VY-x on
> my Lenovo T520 (Sandybridge). IT has been running for a few months
> with the Intel GPU patches and now WITH_NEW_XORG and WITH_KMS. The
> current system is 9.1-BETA1 installed yesterday.
> 
> If I enable "Virtualization" in BIOS, the system boots and runs fine,
> but if I start Xorg and Gnome, I get several windows including
> terminal windows and gkrellm up, but after a few seconds, the display
> freezes. The only thing I have been able to do is to power it down. I
> then disabled "Virtualization again, and all is well.
> 
> Any idea on what other information I can dig up? It's not critical as
> I only use VirtualBox to boot Windows 7 when I need Visio or something
> else that is only available on Windows.(No, no serial console. Darn!)

SandyBridges has several absolutely show-stopper erratas for interoperation
of VT-d engine and GPU. Linux disables several features, including RC6
and fake PPGT, when it detects that VT-d is active for GPU PCI device.
And even then, it seems to still exhibit problems, last time I watched.

Since FreeBSD has no VT-d driver, we cannot know the state of VT-d. Just
disable it if you want to use GPU.
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