[Intel-gfx] unbinding graphics driver

[Andrew Lutomirski]

On Wed, Oct 5, 2011 at 9:38 AM, Jesse Barnes <jbarnes at virtuousgeek.org> wrote:
> On Tue, 4 Oct 2011 18:50:18 -0700
> "Kay, Allen M" <allen.m.kay at intel.com> wrote:
>
>> I'm working on assigning Intel graphics to a guest OS in Xen/KVM environment.  Before assigning the device to the guest OS, I need to first unbind the i915 driver from the device in the host kernel.
>>
>> If I unbind the i915 driver  by doing "echo -n 0000:00:02.0 > /sys/bus/pci/devices/0000:00:02.0/driver/unbind", I get a kernel oops with no stack trace.  Is this something theoretically allowed?
>
> It can be unloaded, but you also have to unbind it from the console:
> $ echo 0 > /sys/class/vtconsole/vtcon1/bind # or whatever is your fbcon
>
> and of course it has to be unused.  You can't unbind it if X is running
> for example.  That said, I've never tested the unbind functionality as
> above, I only ever unload the module.  So we could have undiscovered
> bugs there.
>
>> I have also tried to prevent the i915 driver from loading by renaming the drm directory in /lib/modules to drm.0.  However, i915 driver is still loaded from somewhere, I don't know how it can happen.  Is there a easy way to disable the i915 driver in the kernel?
>
> Probably getting loaded by your initrd image.  After you've renamed it
> in /lib/modules (or removed it) you can re-generate your initrd using
> mkinitrd or mkinitramfs (depending on distro).
>

Alternatively, you can take advantage of one of my favorite
misfeatures.  Boot with i915.asjkdhfjklasehf=1 and i915 will fail to
load :)

--Andy