Re: Graphical glitches (not refreshing?) with Linux's xe driver + Xen 4.19

[Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>]

On Tue, Feb 10, 2026 at 07:06:20PM +0100, Marek Marczykowski-Górecki wrote:
> Hi,
> 
> Recently I started testing compatibility with Intel Lunar Lake. This is
> the first one that uses "xe" instead of "i915" Linux driver for iGPU.
> I test it with Qubes OS 4.3, which uses Xen 4.19.4 and PV dom0 running
> Linux 6.17.9 in this test.
> The result is rather sad:
> https://openqa.qubes-os.org/tests/166691#step/simple_gui_apps/30
> or
> https://openqa.qubes-os.org/tests/166700#step/desktop_linux_manager_config/42
> 
> The black windows are mapped from a domU (using grant tables). But if
> you watch the video (in the "logs&assets" tab), login window of dom0 is
> affected too (background is rendered significantly later than its text
> and widgets). 
> 
> I didn't found any relevant errors in kernel (or Xen) messages. Just in
> case, full dumps:
> https://openqa.qubes-os.org/tests/166700/file/desktop_linux_manager_config-journalctl.log
> https://openqa.qubes-os.org/tests/166700/file/desktop_linux_manager_config-xl-dmesg.log
> 
> Some user reported similar issue with Intel Arc Pro B50, which also uses
> "xe" driver:
> https://github.com/QubesOS/qubes-issues/issues/10661
> 
> I tested also Linux 6.19-rc8, no improvements.
> 
> My previous tests of the xe driver on older systems (Meteor Lake, Raptor
> Lake) resulted in similar behavior, while i915 works fine there. But there
> I needed to use force_probe parameter, and blamed the issue on xe not
> officially supporting those platforms. I wanted to compare with i915 on
> LNL, but i915 doesn't support that model at all (and if I force it, I
> get kernel panic in i915_pci_probe...).
> 
> Interestingly, it appears to work just fine on Qubes OS 4.2 (Xen 4.17.6,
> same Linux dom0 version). I did not tested with Xen 4.21.
> 
> In both cases, our Xen has the patch to use Linux's PAT layout applied.
> That's a workaround for
> https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/7648, which is
> fixed now, but apparently similar bug is still present in a few other
> drivers (including binary nvidia one...).
> 
> The same Linux kernel started without Xen works just fine.
> 
> Any ideas?
> 
> Having good and a bad version, I can try to bisect this one, but given
> it requires rebuilding Xen toolstack each time too (due to bisection
> across releases), I'd rather avoid it if possible...
> 
> I'm CC-ing also intel-xe list, maybe somebody there have some ideas how
> to debug this. 

Unfortunately I'm afraid we don't have any good advice here.

First I thought about trying to isolate Mesa version in the Qubes OS
version, but the fact that it works in bare metal makes this a silly
option.

It looks more a cache management indeed, and I'm afraid we will
only find the definite spot after the bisect :(

> 
> -- 
> Best Regards,
> Marek Marczykowski-Górecki
> Invisible Things Lab