Re: Graphics pass-through

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2011-05-05 17:17, Alex Williamson wrote:
>> And what about the host? When does Linux release the legacy range?
>> Always or only when a specific (!=vga/vesa) framebuffer driver is loaded?
> 
> Well, that's where it'd be nice if the vga arbiter was actually in more
> widespread use.  It currently seems to be nothing more than a shared
> mutex, but it would actually be useful if it included backends to do the
> chipset vga routing changes.  I think when I was testing this, I was
> externally poking PCI bridge chipset to toggle the VGA_EN bit.

Right, we had to drop the approach to pass through the secondary card
for now, the arbiter was not switching properly. Haven't checked yet if
VGA_EN was properly set, though the kernel code looks like it should
take care of this.

Even with handing out the primary adapter, we had only mixed success so
far. The onboard adapter worked well (in VESA mode), but the NVIDIA is
not displaying early boot messages at all. Maybe a vgabios issue.
Windows was booting nevertheless - until we installed the NVIDIA
drivers. Than it ran into a blue screen.

BTW, what ATI adapter did you use precisely, and what did work, what not?

One thing I was wondering: Most modern adapters should be PCIe these
days. Our NVIDIA definitely is. But so far we are claiming to have it
attached to a PCI bus. That caps all the extended capabilities e.g.
Could this make some relevant difference?

Jan

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