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Good news! I did some testing with Ubuntu 14.04 beta2 and Xen 4.4.

Using xl and qemu-xen, the installation of Windows 7 on the domU went without an issue, so did the AMD driver installation. Trying out passthrough did not work - yellow triangle in Windows device manager with an insufficient resources message.

I changed to qemu-xen-traditional and the Windows guest rebooted without an issue into a passed through desktop. Several reboots later, all looks fine, except the low Windows Aero WEI. Could be that using qemu-xen during Windows installation did something to the Aero performance?

The only two glitches I encountered were:

1. Using Ubuntu Gnome edition, it would detect both graphics cards during installation and set them up for dual screen. Solution: Install only one graphics card (for dom0), install Xen, passthrough the PCI IDs of the second (yet to be installed) card via pciback using the initramfs method, shutdown, install card, reboot.

2. Both xtightvncviewer and vnc4viewer have bugs. The first one doesn't accept empty passwords @*^&$$%%@@@-*. What a pain in the neck! I had to give a 6-8 letter password in the domU.cfg file to make it work.

The vnc4viewer displays a different issue: It sometimes crashes after start. At some point during Windows installation, it would always crash and I had to remove it.

Possible workaround could be installing some xen tools (can't remember the name, but it includes libvirt and some other tools, including a vncviewer - haven't tested it).

Summary: The new Xen 4.4 with a 3.13 kernel and xl using qemu-xen-traditional works with AMD cards (at least with the 6450). It doesn't display any of the symptoms of earlier releases. Multiple reboots of the domU do not influence stability or performance of dom0, nor of domU. I have run the WEI assessment several times, after domU reboots, it's the same.

Installing the GPLPV drivers improved disk performance according to WEI (from 5.5 to 5.9 for an external USB HDD), network performance and other things are not tested by WEI.

Now let's just hope that no-one messes this up.

I also hope that devs perhaps backport the improvements/bug fixes to earlier Xen 4.3 releases.

On Thursday, April 10, 2014 9:44 AM, H. Sieger <powerhouse.linux@xxxxxxxxx> wrote:

Thanks for the contact details and suggestions. Before turning to xen-devel, I will give Xen 4.4 a spin and see how that works. I believe the new Ubuntu 14.04 comes with Xen 4.4 in which case I won't even have to build it.

One more thing: All my testing was done on Linux Mint / Ubuntu and I can't really tell if this is a Ubuntu specific issue. If others have used the AMD 7770 or AMD 6450 cards for VGA passthrough and had more success with Xen 4.2 or Xen 4.3, I would be interested to hear.

On Wednesday, April 9, 2014 2:08 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:

On Wed, 2014-04-09 at 03:40 -0700, H. Sieger wrote:
> I'd be glad to be brought in touch with the AMD people to get this
> resolved, and I'm willing to help out where I can (time permitted).

I think your best bet is to start a thread on xen-devel about the issues
you are having and take it from there. Kelly.Zytaruk@xxxxxxx is the one
working on this so probably CC him too.

It would probably be best to try at least Xen 4.4 if not the development
branch since things will need to be fixed there and then considered for
backporting.

For xen-devel please post plain text instead of HTML and avoid
top-posting.

Ian.

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Re: [Xen-users] AMD cards - VGA passthrough no more possible with newer Xen / kernel releases