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I have a Ubuntu 15.10 based PC with two different ATI/AMD graphics cards (ATI Radeon 4650 and AMD 7970) I want to install Windows via qemu/kvm with vga passthrough. For this I have to blacklist the AMD 7970 card using the command blacklist radeon. Unfortnately the radeon driver ist used for both cards, so I am afraid of blacklisting both cards. What coudl I do to circumvent this problem.

thanks in advance.

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One solution would be to let EITHER vfio-pci OR pci-stub (depends on whether you use the newer -device vfio-pci or older -device pci-assign) bind the card for passthrough first.

Depends on whether you load either of the modules and/or radeon in the initramfs, you might need to use a softdep in /etc/modprobe.d to make sure radeon is loaded later than the passthrough module. (Like if you load vfio-pci in the initramfs but not radeon, you don't need the softdep. If you load both vfio-pci and radeon in the initramfs OR both NOT in the initramfs, you probably need the softdep.

For example:

/etc/modules-load.d/vfio-pci.conf:

vfio-pci

/etc/modprobe.d/radeon.conf:

softdep radeon pre: vfio-pci

/etc/modprobe.d/vfio-pci.conf:

options vfio-pci ids=XXXX:XXXX

The "ids" can be checked by lspci -nn. You may want to add the id of the HDMI Audio device of that card as well. The list is comma-separated (i.e. ids=XXXX:XXXX,YYYY:YYYY)

Btw, as long as you've done this correctly, you don't need to manually re-bind driver with sysfs/echo afterwards.

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  • Thank you very much for your fast response. I will try this tomorrow!
    – stormborn234
    Commented Feb 20, 2016 at 17:13

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