Re: [PATCH v2] gpu: Fix uninitialized buddy for built-in drivers

[Matthew Auld <matthew.auld@intel.com>]

On 19/02/2026 10:16, Danilo Krummrich wrote:
> On Mon Feb 16, 2026 at 12:19 PM CET, Koen Koning wrote:
>> Use subsys_initcall instead of module_init for the GPU buddy allocator,
>> so its initialization code runs before any gpu drivers.
>> Otherwise, a built-in driver that tries to use the buddy allocator will
>> run into a kernel NULL pointer dereference because slab_blocks is
>> uninitialized.
>>
>> Specifically, this fixes drm/xe (as built-in) running into a kernel
>> panic during boot, because it uses buddy during device probe.
> 
> I just noticed that this patch was sent twice, and I posted my feedback on [1]
> -- pasting it here as well.
> 
>> Fixes: ba110db8e1bc ("gpu: Move DRM buddy allocator one level up (part two)")
> 
> This Fixes: tag seems wrong. How is this code move related to this problem?

This popped up as a very recent regression for us internally. It looks 
like it worked before since link order ensured drm_buddy came before all 
the driver code. With above commit the link order changed and became 
drm/ and then buddy. See [1] also, which is maybe clearer to see this.

[1] 
https://lore.kernel.org/intel-xe/20260213152047.179628-1-koen.koning@linux.intel.com/

> 
> This should rather be:
> 
> Fixes: 6387a3c4b0c4 ("drm: move the buddy allocator from i915 into common drm")
> 
> Also, please add:
> 
> Cc: stable@vger.kernel.org
> 
>> Cc: Joel Fernandes <joelagnelf@nvidia.com>
>> Cc: Dave Airlie <airlied@redhat.com>
>> Cc: intel-xe@lists.freedesktop.org
>> Cc: Peter Senna Tschudin <peter.senna@linux.intel.com>
>> Cc: Matthew Auld <matthew.auld@intel.com>
>> Signed-off-by: Koen Koning <koen.koning@linux.intel.com>
> 
> [1] https://lore.kernel.org/all/DGIUUFLC31D5.2OZBF5FWQJWMZ@kernel.org/