Re: AMD GPU passthrough in Xen

[Gordan Bobic <gordan@bobich.net>]

On 2014-09-23 14:45, Sander Eikelenboom wrote:
> Good to know there is interest from AMD into this area :-)
> 
> I'm experimenting for a while with:
> 
> - xen-unstable (and thus xl)
> - latest kernels (both dom0 and domU)
> - qemu-xen
> - Radeon HD 6570
> - secondary passthrough
> - Debian linux (sid) with the opensource (in kernel) radeon driver
>   (i also tried fglrx with succes, but it's a real PITA to build with 
> every
>   new kernel, so i ditched that)
> 
> It used to work, but something broke at the moment, but that could also 
> be the
> changes to the systemd cruft that Debian jessie/sid is currently 
> undergoing (or
> something else since i regularly update all components).
> 
> The problems are mostly with restarting the domU, it differs a bit:
> - sometimes screen goes ok, sometimes it's garbage.
> - the radeon powercontrols only seem to work on the first boot and
> give errors on any subsequent one.
> 
> But when it works it does:
> - the powercontrol.
> - opengl and opencl benchmarks with (near) native results.
> - hardware video acceleration in xbmc for instance.
> 
> So one of the main problems at present seems to be proper resetting of
> the whole
> device on domain shutdown/start. I did do some experiments with the 
> opensource
> radeon driver, but didn't get conclusive results out of that yet.

Interestingly, on my machine this seems to be down to the lack of
reset knowledge on part of xen-pciback. In dom0:

# lspci -nn | grep ATI
0e:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. 
[AMD/ATI] Caicos [Radeon HD 6450/7450/8450] [1002:6779]
0e:00.1 Audio device [0403]: Advanced Micro Devices, Inc. [AMD/ATI] 
Caicos HDMI Audio [Radeon HD 6400 Series] [1002:aa98]

# ls -la 
/sys/devices/pci0000:00/0000:00:03.0/0000:0a:00.0/0000:0b:00.0/0000:0e:00.0/reset
--w------- 1 root root 4096 Sep 23 15:39 
/sys/devices/pci0000:00/0000:00:03.0/0000:0a:00.0/0000:0b:00.0/0000:0e:00.0/reset

# cat 
/sys/devices/pci0000:00/0000:00:03.0/0000:0a:00.0/0000:0b:00.0/0000:0e:00.0/d3cold_allowed
1

# uname -a
Linux normandy 3.14.12-1.el6xen.x86_64 #1 SMP Fri Jul 11 19:30:39 EST 
2014 x86_64 x86_64 x86_64 GNU/Linux

But IIRC if I unbind the radeon (open source) driver and bind
xen-pciback to the device, the reset node disappears (not in a
position to try it right now).

Gordan