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Re: [Xen-devel] AMD GPU passthrough in Xen

  • To: xen-devel@xxxxxxxxxxxxx
  • From: Gordan Bobic <gordan@xxxxxxxxxx>
  • Date: Tue, 23 Sep 2014 15:44:16 +0100
  • Delivery-date: Tue, 23 Sep 2014 14:44:32 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xen.org>

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

# 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).


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