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?
