Re: Struggling with PCI-Passthrough

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 10/03/14 09:59, Alexander Brychcy wrote:
> Hi,
>
> I'm currently trying to create a Windows 7 HVM with GPU Passthrough.
>
> My setup is the following:
> CPU:	Xeon E3-1230v3
> Board:	Asus P9D-E/4L
> RAM:	16GB Kingston from Board QVL
> GPU:	Sapphire R9 270X 4GB
>
> The passthrough itself is working (Tested with Debian Wheezy dom0 on Xen
> 4.1, then XenServer 6.2 and now Debian Jessie dom0 on Xen 4.3)
>
> Under Debian Jessie i was not able to passthrough the USB Controller,
> although it appeard at xl pci-assignable-list and i cannot assign more
> than 2GB of memory to the HVM.
>
> The overall problem is, that the HVM starts up and is running fine. But
> after a unspecific amount of time the hole system freezes. The cursor in
> dom0 still blinking, but no input possible - not even in xen serial
> console. I had one run, without a freeze, but the GPU performance was
> very poor, so i tried a manual reset. After the HVM reboot the
> performance was as expected, but soon the system froze again.
>
> I'm not sure, if this problem is related to Xen, because i tried to
> create the virtual machine with KVM and had the same issue. But i
> switched to Xen to get the best performace.
>
> I will add my config and log files and hope you can help me to get this
> setup fully working.
>
> Kind regards,
> Alexander

Looking at the serial log, it would appear that Xen has decided to
schedule no vcpus whatsoever, and is completely idle.

Looking at the 'Q' output, only two vcpus (one from each domain) are not
in a blocked state, but no obvious reason for them to be blocked; they
are not blocked waiting for events.

Are you able to try this with a debug version of Xen?  Perhaps an
assertion will be tripped which might give more of a clue.

It is certainly interesting that the same behaviour exists with KVM,
suggesting it is something to do with hardware interaction, but I can
see no obvious reason why Xen is as idle as it is.

~Andrew