Setting Up A Xen Graphics Card Pass-Through

[gilboa]

@Xaseron,
Please do.
What's you setup?
Did you use stock Xen or (as the OP) highly patched one?
Did you require the VGA BIOS image?

Thanks,
Gilboa

[Xaseron]

My Setup:
AMD FX-820
ASUS M5A99X Evo
Sapphire Radeon HD4550 (dom0)
Sapphire Radeon HD6870 (domU)
OS: Archlinux

From the XEN wiki:

Qemu-dm emulator used in the Xen HVM guest needs to disable the internal (emulated) graphics adapter, copy and map the real graphics adapter VGA BIOS to the virtual machine memory, emulate and execute it there to reset and initialize the graphics card properly, map and passthru the VGA adapter real memory to the HVM guest, passthru all the legacy IO-port and legacy memory ranges from the HVM guest to the real graphics adapter etc.

I think copying the graphic bios is only need if you want to replace the emulated card. I only attach my graphic card like a normal pci device. I installed the OS and the gaphic driver normally over VNC. After the reboot the catalyst drives takes care of disabling the incompatible graphic card, the emulated one and switches the video output to the passthrough device. It should work with an appropriate xorg.conf too.

At first i used plain Xen 4.1.2 without any patches. But due an avx bug in glibc i had to apply 3 patches(24341, 24344, 24345) from unstable and add "xsave=1" to the hypervisior boot options. I think the patches are only needed on AVX capable cpus.

For completeness my configs:
grub2: http://pastie.org/3673593
xen-domu: http://pastie.org/3673572 mostly like the default config

Unfortunately, the powermanagement is not working with an AMD Bulldozer. But this will hopefully come in Linux 3.4 :-)

[Djhg2000]

I've been running Debian and Vista (don't ask) like this for a few months now ( http://www.tomshardware.co.uk/forum/...irtual-machine ), as I upgraded my CPU around christmas. It feels like the graphics performance has actually increased, but I think that was because my old E2160 bottlenecked my HD5850 a bit. Every game I've tried so far works very well and as someone said you completely forget you're in a VM.

Most noticeably, switching between the dom0 and domU with my hybrid synergy and dual mouse setup is really easy and the sense of control is something I just can't describe with words. It's something that needs to be experienced.

[evanjfraser]

Thanks guys for posting your experiences/configs here, it certainly helped clear things up for me.

As it happens I've just bought the same ASUS mobo with the hopes of setting this up too.

I do still need to pick up another cheap vid card for running the linux vm though.

Evan.

[gilboa]

Xaseron,

Thanks for the info.
I'm on nVidia, so my experience will most likely differ from yours, but I'll free some time to try it out.

- Gilboa

[powerhouse]

If anyone still reads this thread: The advise given by Michael to use Teo Ming's tutorial should be followed as a last resort! I don't want to downplay the efforts of Teo Ming, but in many cases it's much easier to get the same results with Xen. Some suggestions have been posted above.

Given the right hardware, Xen VGA passthrough is almost a no-brainer. And the performance is outstanding, both on the Linux dom0 side and the Windows guest side.

Teo Ming's tutorial may be relevant to those users who try to passthru a Nvidia graphics card. Only very few Nvidia cards are supported under Xen natively (Xen 4.2 has improved on that). Furthermore, passing through a secondary GPU is much easier, as has been noted before.

Just my 2 cents.