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

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 
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.


Tuesday, September 23, 2014, 3:19:41 PM, you wrote:

> Hi Peter / Sander,

> Yes, I have AMD GPU passthru working as both primary and secondary passthru.  
> Secondary was easy but primary is a bit tricky.  

> Getting on to your questions;

>> Is there any specific reason you're using Xen 4.2 rather than 4.4.1?

> I am working on a project that is based on Xen 4.2 (I can't say any more than 
> that).  I have looked at some of the more recent versions just to check if 
> some of the bugs that I have seen have been fixed but I have not studied the 
> newer versions in detail.  At some point in time in the future I would like 
> will make the jump to a more recent version but I don't know the scheduling 
> of that.

>> In 4.2, using xl or xm?

> xl

>> qemu-traditional (with rombios) or "upstream"

> qemu-traditional

>> Primary or secondary passthrough?

> Both but I am focusing on secondary right now.

>> Presumably 64 bit versions of Windows?

> 32 bit and 64 bit Win7.  I have tested Win8.1 and it works but my focus is 
> currently Win7

>> I am quite willing to test various scenarios. I've a 6950, 6450 and 5450.

> Awesome.  My goal right now is obtaining stability on Xen 4.2.  Since 4.2 is 
> past its feature cutoff I won't be able to submit any open source changes for 
> it.  I would like to eventually work with the community to get passthru 
> working with a recent version of "upstream".  

> Thanks,
> Kelly

>> -----Original Message-----
>> From: Sander Eikelenboom [mailto:linux@xxxxxxxxxxxxxx]
>> Sent: Monday, September 22, 2014 8:38 AM
>> To: Peter Kay
>> Cc: xen-devel@xxxxxxxxxxxxx; Zytaruk, Kelly
>> Subject: Re: [Xen-devel] AMD GPU passthrough in Xen
>> Monday, September 22, 2014, 2:16:58 PM, you wrote:
>> > Hi Kelly, list
>> > I see you're having AMD GPU success with Xen 4 2 and Linux 3.4.9. I've been
>> less than successful getting passthrough working at all in Xen (although 
>> it's fine
>> in KVM primary passthrough as long as the BIOS is supplied as a file). Could 
>> I
>> confirm the following :
>> > Is there any specific reason you're using Xen 4.2 rather than 4.4.1? I 
>> > know in
>> some ways 4.4 suffers as it's now xl only and some of the xm functionality 
>> has
>> not come across.
>> > In 4.2, using xl or xm?
>> Another interesting question/aspect would be qemu-traditional (with rombios)
>> or "upstream" (with seabios) ?
>> > Primary or secondary passthrough?
>> > Presumably 64 bit versions of Windows?
>> > My system is a bit old (Core2Quad) but as mentioned AMD passthrough works
>> in KVM but I've found it tricky in Xen.
>> > I am quite willing to test various scenarios. I've a 6950, 6450 and 5450.
>> > Thanks
>> > Peter

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