Re: [regression] Re: Linux 6.12.75

[Vitaly Chikunov <vt@altlinux.org>]

Thorsten,

On Mon, Apr 13, 2026 at 05:17:30PM +0300, Vitaly Chikunov wrote:
> Thorsten, Sasha,
> 
> On Mon, Apr 13, 2026 at 01:33:18PM +0200, Thorsten Leemhuis wrote:
> > On 4/2/26 10:44, Vitaly Chikunov wrote:
> > > Sasha,
> > > 
> > > 1. I cannot find this commit posted on lore.kernel.org to report to
> > > exact patch.
> > > 
> > > | From: Matt Roper <matthew.d.roper@intel.com>
> > > | Date: Tue, 10 Sep 2024 16:47:29 -0700
> > > | Subject: [PATCH 6.12/sisyphus] drm/xe: Switch MMIO interface to take xe_mmio
> > > |  instead of xe_gt
> > > | 
> > > | [ Upstream commit a84590c5ceb354d2e9f7f6812cfb3a9709e14afa ]
> > > | 
> > > | Since much of the MMIO register access done by the driver is to non-GT
> > > | registers, use of 'xe_gt' in these interfaces has been a long-standing
> > > | design flaw that's been hard to disentangle.
> > > [...]
> > > 
> > > 2. After this patch applied to 6.12.75 there is kernel NULL pointer
> > > dereference BUG on MSI MAG H670 12th Gen Intel(R) Core(TM) i5-12600K
> > > with ASRock Intel Arc B580 Challenger [Alchemist], 12GB:
> > > [...]
> > > The commit is found not by a git bisect (since it's reported by end
> > > user and I cannot reproduce it on my hardware) but (by analyzing dmesg)
> > > with:
> > > [...]
> > > Then finding the suspecting commit:
> > > 
> > >   $ git log --oneline -G'XE_LUNARLAKE' v6.12.74..v6.12.75
> > >   26a40327c25c drm/xe: Switch MMIO interface to take xe_mmio instead of xe_gt
> > > 
> > > 6.18 and above are not affected by the bug. Also, they have another commit
> > > modifying the line which is not present in 6.12 branch:
> > > [...]
> > > Related drm/xe bug report https://gitlab.freedesktop.org/drm/xe/kernel/-/work_items/7661
> > Nobody reacted to this and it seems the gitlab ticket is stalled, too.
> > So let me ask: can this be resolved by reverting 26a40327c25c in 6.12.y?

It's turned out these two commits are revertible together:

  8f6848b2f6ea ("drm/xe/mmio: Avoid double-adjust in 64-bit reads")
  26a40327c25c ("drm/xe: Switch MMIO interface to take xe_mmio instead of xe_gt")

I am going to ask the users to test this.

Thanks,

> 
> As of me, this is not easy to revert, as it depends on many other
> commits, and git does not have tooling to determine all dependant
> commits for revert. I hope someone from drm subsystem notices this to
> work on it, or Sasha can pull missing commits or revert this (obviously,
> he have tooling for this, but I was unable to find it). [I found
> obsolete references to deps but is seems not used for years and Python
> git-deps tool seems broken.]
> 
> What I found is, offending commit is picked due to
> 
>   Stable-dep-of: 4a9b4e1fa52a ("drm/xe/mmio: Avoid double-adjust in 64-bit reads")
> 
> Which, perhaps, needs to be reverted.
> 
> Offending commit 26a40327c25c is not tracked in lore.
> It's part of 9 piece patchset, perhaps they are logically dependent too,
> so need to be reverted together.
> 
> The possible fix is part of 6 piece patchset, which does not cherry-pick
> easily due to conflicts.
> 
> If someone can produce correct fix we can participate in the tests.
> 
> Thanks,
> 
> > 
> > Ciao, Thorsten