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

["H. Sieger" <powerhouse.linux@xxxxxxxxx>]

Thanks Daniel,

I'm aware of the changes required in the guest.cfg file when using xl versus xm. Still, I had no luck with xl and the 6450 and the 7770.

It is my understanding that qemu-xen (the upstream qemu) doesn't support yet VGA passthrough, is that correct?

On Wednesday, April 9, 2014 7:02 PM, Daniel Shub <Daniel.Shub@xxxxxxxxxxxxxxxx> wrote:

While it is not always easy and I am not an expert by any means, a number of people have had success passing through AMD devices with the XL tool stack. I have passed through my AMD 5450, obviously not the most recent or high end, but solid none the less, with the XL tool stack from an Arch Linux Dom0 with Xen 4.2, 4.3, and 4.4 to both Linux (Debian and Arch) and Windows (XP) DomUâs. At some point, I cannot remember if it was the change from Xen 4.2 to Xen 4.3 or an upgrade to QEMU, it became necessary to add âdevice_model = 'qemu-xen-traditional'â to the configuration file. Most of the how-to guides online are out of date in this regard. I have found this list really helpful in solving my problems.

 

Dan

 

 

From: xen-users-bounces@xxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxx] On Behalf Of H. Sieger
Sent: 09 April 2014 08:37
To: xen-users@xxxxxxxxxxxxx
Subject: [Xen-users] AMD cards - VGA passthrough no more possible with newer Xen / kernel releases

 

I've recently tested both my AMD HD 7770 and my AMD HD 6450 video cards for VGA passthrough and had a hell of a time getting it working. Here the results of my tests:

 

1. Kernel 3.11.0-19-generic with Xen 4.3.0 and xm toolstack

dom0 OS: Linux Mint 16 (based on Ubuntu 13.10), kernel info see above

domU: Windows 7 Pro 64 bit

GPU for VGA passthrough: Sapphire HD 6450 (AMD), secondary passthrough

Method: xen-pciback module loaded from initramfs:

echo "xen-pciback passthrough=1 hide=(02:00.0)(02:00.1)" >> /etc/initramfs-tools/modules

Result with xm create /etc/xen/win7.cfg:Error: (22, 'Invalid argument')

 

The same win7.cfg file with a Nvidia Quadro 2000 works perfectly. Other Xen users have reported the same problem, see here.

 

2. Kernel 3.11.0-19-generic with Xen 4.3.0 and xl toolstack

dom0 OS: Linux Mint 16 (based on Ubuntu 13.10), kernel info see above

domU: Windows 7 Pro 64 bit

GPU for VGA passthrough: Sapphire HD 6450 (AMD), secondary passthrough

Method: xen-pciback module loaded from initramfs:

echo "xen-pciback passthrough=1 hide=(02:00.0)(02:00.1)" >> /etc/initramfs-tools/modules

I was able to start the Windows installation in domU but after a domU reboot it wouldn't start:

> xl create /etc/xen/win7.cfg
Parsing config from /etc/xen/win7.cfg
WARNING: specifying "tsc_mode" as an integer is deprecated. Please use the named parameter variant. e.g. tsc_mode="default"
WARNING: ignoring "kernel" directive for HVM guest. Use "firmware_override" instead if you really want a non-default firmware
xc: info: VIRTUAL MEMORY ARRANGEMENT:
  Loader:        0000000000100000->00000000001a69a4
  Modules:       0000000000000000->0000000000000000
  TOTAL:         0000000000000000->00000000ff800000
  ENTRY ADDRESS: 0000000000100608
xc: info: PHYSICAL MEMORY ALLOCATION:
  4KB PAGES: 0x0000000000000200
  2MB PAGES: 0x00000000000003fb
  1GB PAGES: 0x0000000000000002
libxl: error: libxl_device.c:894:device_backend_callback: unable to add device with path /local/domain/0/backend/vbd/3/768
libxl: error: libxl_create.c:932:domcreate_launch_dm: unable to add disk devices
libxl: error: libxl_dm.c:1300:libxl__destroy_device_model: could not find device-model's pid for dom 3
libxl: error: libxl.c:1409:libxl__destroy_domid: libxl__destroy_device_model failed for 3
libxl: error: libxl_device.c:894:device_backend_callback: unable to remove device with path /local/domain/0/backend/vbd/3/768
libxl: error: libxl.c:1445:devices_destroy_cb: libxl__devices_destroy failed for 3

I've been trying different options with the win7.cfg file in conjunction with xl. I had to reboot (hard reset) the PC each time I shut down the Windows domU (what a pain in the neck).

In short, the xl toolstack in Xen 4.3.0 is totally useless with VGA passthrough and at least 2 AMD cards: HD 6450 and HD 7770.

I tried resetting the GPU in the domU which then prevented the domU from switching to the secondary graphics display (the HD 7770 or HD 6450).

 

3. Kernel 3.2.0-23-generic with Xen 4.1.2-2ubuntu2 and xm toolstack

dom0 OS: Linux Mint 13 (based on Ubuntu 12.04), kernel info see above

domU: Windows 7 Pro 64 bit

GPU for VGA passthrough: Sapphire HD 6450 (AMD), secondary passthrough

Method: xen-pciback module loaded from initramfs.

The same AMD cards work just perfect with the xm toolstack, kernel 3.2.0-23-generic and Xen 4.1.2-2ubuntu2 on a Linux Mint 13 dom0, after downgrading both the kernel and Xen to the earliest release. Somewhere down the kernel/Xen upgrade path things went wrong. See here and here.

 

Conclusion and questions:

With xm deprecated and xl not up to snuff, what's the future of VGA passthrough under Xen?

 

Does anyone here have a solution? It can't be that AMD users have to use ancient kernel and Xen releases with a deprecated xm toolstack to enjoy VGA passthrough. Or does Xen 4.4 answer these issues and work with xl and AMD cards?

 

P.S.: I would file bug reports but it seems pointless, there are just too many things going wrong. The error 22 with xm should have been solved long ago, and yes, I checked the python code and the bug fix has been applied in Xen 4.3.0, yet there is again the infamous error 22 message.

As to the domU shutdown/reboot issue with xl it has been reported many times. The only thing I haven't read yet is that someone is trying to fix this. Or is there actually a fix or release that works?

This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please send it back to me, and immediately delete it.   Please do not use, copy or disclose the information contained in this message or in any attachment.  Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham.

This message has been checked for viruses but the contents of an attachment may still contain software viruses which could damage your computer system, you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation.

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxx
http://lists.xen.org/xen-users