Re: [Xen-users] Help with VGA passthrough

[Gordan Bobic <gordan@xxxxxxxxxx>]

On 2014-06-25 09:45, Daniel E. Shub wrote:
> On Wednesday 25 June 2014 08:45:07 Gordan Bobic wrote:
>
> > In terms of device capture, reboot the machine and look at lspci
> -vvv. If
>
> > anything other than pciback is the driver attached to your GPU, it
> isn't
>
> > going to work. If the radeon driver touched the card it has been
> tainted
>
> > and until the bus reset method is implemented it won't work. You
> will need
>
> > to remove the radeon driver from your initrd, blacklist it in
> > /etc/modprobe.d/, create a configuration file for xen-pciback in
> there to
>
> > make it capture the PCI devices you will be passing through, and
> create a
>
> > script in /etc/sysconfig/modules/ to modprobe xen-pciback and AFTER
> that
>
> > modprobe radeon if your primary GPU also uses that driver.
> I don't have to do any of this with my 5450. My machine has two 5450's
> and no other video cards so maybe that is why it works. I let my
> machine boot up as normal and then just use xl pci-assignable-add
> before I want to start a DomU with the video card as secondary
> passthrough.
Does your machine load the radeon driver? If you don't boot into
GUI and have the radeon driver blacklisted then most of this
wouldn't matter. I quite clearly remember that if anything touched
the GPU before the domU driver it wouldn't work at all. It is
plausible something has changed since I tried it, though, such
as the radeon driver in dom0 resetting the card to a clean state
when it unloads.

Gordan

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