[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-users] Problems with VGA Passthrough

On 07/08/2013 05:20 PM, Paolo Cancedda wrote:
Hello Javier,

On Wed, Jul 3, 2013 at 10:56 PM, dkeruza <dkeruza@xxxxxxxxx
<mailto:dkeruza@xxxxxxxxx>> wrote:

    I ended up compiling xen 4.1.4 with patches for VGA Passthrough
    Check this message for info.

following your advice, I was able to see VGA Passthrough working for the
very first time.
I compiled Xen 4.1.4 after applying the patches here:
The installation was a bit messy, since makefiles of 4.1.4 did not honor
PREFIX variable.
USB passthrough does not seem to work, I used PCI passthrough of one of
the two EHCI controllers on the motherboard.
Unfortunately, however, with this setup my VMs are quite unstable.
A Windows 8 VM reboots after waiting for some time after boot, before
logging in.
A Windows 7 VM at first seemed to work, but it stopped responding after
being left alone for a few minutes (perhaps it's something related to
power management).
Do you know why these patches are not on Xen development tree (yet)?

I have it all working stably with 4.2.2 with only the XSA patches (using RPMs from the CRC repository). I am also using PCI passthrough for a USB controller (I have two USB ports on the same physical controller, which is handy as I only have to pass in one USB controller).

If you are using > 2GB of RAM in domU this is going to cause you the sort of instability that will drive you nuts - it certainly did for me, and the only reason I persevered in the face of extreme frustration is because KVM didn't work for me with VGA passthrough _at all_, and ESX was a non-starter due to my hardware's lack of ACS capable PCI bridges which according to documentation, ESX needs for PCI passthrough. DomUs with > 2GB of RAM are not going to work with passing through devices with large BARs such as GPUs. A fix for this bug is in 4.3, due out any day now.

I had mixed luck with ATI passthrough, I'm using quasi-Quadro cards (GeForce modified into Quadro, see here for some details:


Since the article I've moved further with the quasi-Quadros, I currently have a GTX470 (Quadro 5000) and a GTX480 (Quadro 6000) passed through to two separate VMs, and this is working lovely. No performance degradations or host crashes with domU reboots any more. As far as I can tell, judging by what ended up in dom0 syslog, the crashes were caused by PCI memory overwrites (AER errors all over the logs, search the archives for my previous reports on the subject). I am not sure why the host crashes have actually stopped when rebooting VMs, but when I got the 2nd VGA passthrough domU set up, the problem just went away. All in all, I'm finding quasi-Quadros just work a lot better than ATIs in terms of how they handle domU restarts and re-initialization.

I'm currently using an 8800GT card for dom0, but am hoping to switch to an ATI 4850, purely so that I can make my life easier by blacklisting all the nvidia drivers and not having the complication of selective pre-emptive partial detaching of Nvidia devices before the nvidia driver loads. Unfortunately, cards later than ATI 4xxx are unusable for me due to only having one DL-DVI capable port (one of the insurmountable reasons why Nvidia is the only option for me at the moment).


Xen-users mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.