Re: [XEN PATCH] tools/libs/light/libxl_pci.c: explicitly grant access to Intel IGD opregion

[Jason Andryuk <jandryuk@gmail.com>]

On Tue, Apr 5, 2022 at 9:31 PM Chuck Zmudzinski <brchuckz@netscape.net> wrote:
> Correction (sorry for the confusion):
>
> I didn't know I needed to replace more than just a
> re-built i915.ko module to enable the patch
> for testing. When I updated the entire Debian kernel
> package including all the modules and the kernel
> image with the patched kernel package, it made
> quite a difference.
>
> With Jason's patch, the three call traces just became a
> much shorter error message:
>
> Apr 05 20:46:18 debian kernel: xen: --> pirq=16 -> irq=24 (gsi=24)
> Apr 05 20:46:18 debian kernel: i915 0000:00:02.0: [drm] VT-d active for
> gfx access
> Apr 05 20:46:18 debian kernel: i915 0000:00:02.0: vgaarb: deactivate vga
> console
> Apr 05 20:46:18 debian kernel: Console: switching to colour dummy device
> 80x25
> Apr 05 20:46:18 debian kernel: i915 0000:00:02.0: [drm] DMAR active,
> disabling use of stolen memory
> Apr 05 20:46:18 debian kernel: resource sanity check: requesting [mem
> 0xffffffff-0x100001ffe], which spans more than Reserved [mem
> 0xfdfff000-0xffffffff]
> Apr 05 20:46:18 debian kernel: caller memremap+0xeb/0x1c0 mapping
> multiple BARs
> Apr 05 20:46:18 debian kernel: i915 0000:00:02.0: Device initialization
> failed (-22)
> Apr 05 20:46:18 debian kernel: i915 0000:00:02.0: Please file a bug on
> drm/i915; see
> https://gitlab.freedesktop.org/drm/intel/-/wikis/How-to-file-i915-bugs
> for details.
> Apr 05 20:46:18 debian kernel: i915: probe of 0000:00:02.0 failed with
> error -22
> --------------------- End of Kernel Error Log ----------------------
>
> So I think the patch does propagate the error up the
> stack and bails out before producing the Call traces,

Thanks for re-testing.

> and...
>
> I even had output after booting - the gdm3 Gnome display
> manager login page displayed, but when I tried to login to
> the Gnome desktop, the screen went dark and I could
> not even login to the headless Xen Dom0 control domain
> via ssh after that and I just used the reset button on the
> machine to reboot it, so the patch causes some trouble
> with the Dom0 when the guest cannot access the
> opregion. The patch works fine when the guest can
> access the opregion and in that case I was able to
> login to the Gnome session, but it caused quite a bit of
> trouble and apparently crashed the Dom0 or at
> least caused networking in the Dom0 to stop working
> when I tried to login to the Gnome session in the
> guest for the case when the guest cannot access
> the opregion. So I would not recommend Jason's
> patch as is for the Linux kernel. The main reason
> is that it looks like it is working at first with a
> login screen displayed, but when a user tries to login,
> the whole system crashes.

I'm a little surprised you still had output from the VM & display with
the i915 driver not binding.  I guess Linux fell back to another VGA
or Framebuffer driver for the display.

However, locking up the host isn't good.  You didn't happen to catch
any Xen or dom0 output when that happened?

Regards,
Jason