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Re: [Xen-users] [Xen VGA Passthrough] AMD R9 290X GPU???

It's possible that the reason mixing multiple cards doesn't work is because ATI drivers allegedly try and initialise cards, even if they're claimed elsewhere.

Most of my attempts so far have been with KVM. With that a HD6950 passes through just fine once a NoSnoop patch is applied, but having a low end Nvidia card in the host Linux breaks things badly.

I've not managed to get the 6950 working in Xen at all, possibly because its BIOS is >64KB. Under KVM it was necessary to supply the extracted BIOS in a file. A GTX480 soft modded to a Quadro 6000 is working fine with both qemu-traditional and qemu upstream, although upstream seems decidedly less stable. That's with an x64 unpatched Windows 8.

I've spent a large amount of time messing around with motherboards, kernels and suchlike and my notes so far are :

1) If your criteria is passthrough of any type, KVM is a better option than Xen. It works and it's also easily possible to identify iommu isolation groups, aiding stability.

2) If you want AMD GPU passthrough, use KVM, it's solid and you'll save yourself a huge amount of pain.

3) Quadro passthrough on Xen is stable, but the official NVidia drivers must be installed, and the adapter must be assigned at VM bootup.

4) Xen's virtualisation seems better, if possibly slower than KVM. Less exceptions and the virtual USB is fairly decent.

5) The number of issues and broken BIOSes in motherboards is huge.

For my next system, I will probably be buying an Intel workstation or server board. It's clear that the more exciting virtualisation improvements are happening on Intel first and being Intel, their BIOSes generally work, even if there are various quirks. I've just been mildly stung by a xw4600 motherboard, which claims to support VT-d, but is broken. Back to the S3210SHLC it is, then - I'm not keen on the maximum 4x PCI-e speed I'm limited to graphics wise, but it does actually work.

(yes, I should run something much more modern, but I'm looking at how the latest Haswell/Haswell EP chips work out before wasting money..)


On 12 September 2014 12:11, Gordan Bobic <gordan@xxxxxxxxxx> wrote:
On 2014-09-12 11:39, Teo En Ming wrote:

You mentioned that you had a pair of AMD R9 290X GPUs. Were you able
to passthrough AMD R9 290X GPU successfully?

I couldn't get them working properly on bare metal on my SR-2,
apparently due to the NF200 PCIe bridges, so I gave up on them.
That is what I was talking about in my previous email. They'll
probably work just fine if you have a motherboard that doesn't
use Nvidia NF200 PCIe bridges.

Previously I had a HD7970 "working". The reason why I say "working"
rather than working, is because domU reboot problems. It worked
fine on the first boot, though.

Unfortunately, I also had other issues, e.g. with multiple ATI
cards in the same machine when they aren't of the same generation
(e.g. HD4850 primary for dom0 and HD7970 secondary for passthrough)
I was seeing various strange crashes. Whether that's due to driver,
BIOS or VBIOS bugs or a combination thereof, I don't know.


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