[Xen-users] can't passthrough video card

[bob evans <b.evans@xxxxxxxxx>]

Hi, I have been trying to find help with a problem I am having passing a video 
card to a Xen domu. I do have VT-d enabled in BIOS and I can pass some PCI 
cards to the domu, but trying to pass my video card results in an error. My 
dom0 is Kubuntu 3.10, the video card I am trying to pass is a Radeon 7970 ghz. 
I am using Xen version 4.3.0(preserve-AS), my motherboard is an Asrock Extreme4 
z87, and my CPU is an Intel i7-4771. 

When I tried to run my HVM for the first time I had the error: "Error: pci: PCI 
Backend  and pci-stub don't own device 0000:02:00.0"

I found that I had to unbind my PCI devices from the Linux kernel drivers and 
bind them to pciback. I found these instructions for doing this:

echo 0000:08:00.0 > /sys/bus/pci/devices/0000:08:00.0/driver/unbind
echo 0000:08:00.0 > /sys/bus/pci/drivers/pciback/new_slot
echo 0000:08:00.0 > /sys/bus/pci/drivers/pciback/bind

These commands worked great for PCI USB controller, I was able to passthrough 
without any problems. When it was time to pass my video card I ran into 
problems. Here is the relevant output of lspci -k

02:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] 
Tahiti XT [Radeon HD 7970/R9 280X]
        Subsystem: Hightech Information System Ltd. Tahiti XT2 [Radeon HD 7970 
GHz Edition]
        Kernel driver in use: radeon
02:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Tahiti XT HDMI 
Audio [Radeon HD 7970 Series]
        Subsystem: Hightech Information System Ltd. Device aaa0
        Kernel driver in use: snd_hda_intel

I was able to unbind the VGA controller with this command: echo -n 0000:02:00.0 
> /sys/bus/pci/drivers/radeon/unbind
I couldn't get it to work with this command: echo 0000:02:00.0 > 
/sys/bus/pci/devices/0000:02:00.0/driver/unbind

This is ok though, because lspci -k now shows:

02:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] 
Tahiti XT [Radeon HD 7970/R9 280X]
        Subsystem: Hightech Information System Ltd. Tahiti XT2 [Radeon HD 7970 
GHz Edition]
02:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Tahiti XT HDMI 
Audio [Radeon HD 7970 Series]
        Subsystem: Hightech Information System Ltd. Device aaa0
        Kernel driver in use: snd_hda_intel

Now I run into the issue I am currently stuck at. When I issue the commands 

echo 0000:02:00.0 > /sys/bus/pci/drivers/pciback/new_slot
echo 0000:02:00.0 > /sys/bus/pci/drivers/pciback/bind

The first command works fine, but the second results in an error: -bash: echo: 
write error: No such device

This is very confusing and frustrating for me because I don't know what else to 
do. I've found posts from other people with the same problem, but I can't find 
a solution to the problem. I also can't unbind my audio device from the kernel 
driver, but I think this issue is not Xen specific. Trying to unbind the audio 
device always results in the terminal hanging. Please help me. 

I have tried using the bind_lib.bash script and the results are the same. For 
the VGA controller it tells me that there is no such device, for the audio 
device it hangs forever.

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