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Hello Gordan,

I would like to hear more, any chance you can share the xen version, and whether you applied any patches? ÂI know you were looking into the primary passthrough patch and also MMIO (in relation to memory stomping). ÂDid you apply those patches and are you using upstream qemu and/or primary passthrough? ÂAny tips on applying the patches would also be great.

Thanks,

~Casey

On Sat, Jul 6, 2013 at 5:11 PM, Gordan Bobic <gordan@xxxxxxxxxx> wrote:

I just wanted to drop a note to say that I have managed to get VGA passthrough working with multiple cards and domUs.

The cards I am using are quasi Quadro 5000 (modified GTX470) and quasi Quadro 6000 (modified GTX480). (Here is an older article about modified GTS450 modified to Quadro 2000 if anyone is interested:
http://www.altechnative.net/2013/06/23/nvidia-cards-geforce-quadro-and-geforce-modified-into-a-quadro-for-virtualized-gaming/ )

This succeeded despite all the PCIe slots being behind NF200 bridges without ACS support.

I now have two VMs with VGA passthrough running, with one card passed through to each one. The OS is EL6, and I am using Xen packages and kernel from the CRC repository.

What is strange, however, is that whereas I had issues with a single VM crashing on reboot with VGA passthrough (and usually taking the host down with it), with two VMs running, I seem to be able to reboot them dozens of times without any crashes, problems, or performance degradation (yes, rebooting VMs with VGA passthrough without rebooting the host and there appears to be no effect on performance with Nvidia Quadro cards). This new found stability could be down to some of the PCI changes, though, with different USB controllers being passed through, and NIC being bridged rather than PCI passthrough since there are now two domUs that have to share it, so it is possible that the PCI memory stomp I am suspecting to be the root cause is getting coincidentally avoided (not that I'm complaining!).

I'm happy to share more details on and off list if anybody is interested.

Gordan

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Re: [Xen-users] Multiple VMs VGA Passthrough Success Report