Re: [PATCH] drm/amdgpu: fix zero-size GDS range init on RDNA4

[Arjan van de Ven <arjan@linux.intel.com>]

On 4/20/2026 11:42 PM, Christian König wrote:
> On 4/20/26 23:57, arjan@linux.intel.com wrote:
>>
>> RDNA4 (GFX 12) hardware removes the GDS, GWS, and OA on-chip memory
>> resources. The gfx_v12_0 initialisation code correctly leaves
>> adev->gds.gds_size, adev->gds.gws_size, and adev->gds.oa_size at
>> zero to reflect this.
>>
>> amdgpu_ttm_init() unconditionally calls amdgpu_ttm_init_on_chip() for
>> each of these resources regardless of size. When the size is zero,
>> amdgpu_ttm_init_on_chip() forwards the call to ttm_range_man_init(),
>> which calls drm_mm_init(mm, 0, 0). drm_mm_init() immediately fires
>> DRM_MM_BUG_ON(start + size <= start) -- trivially true when size is
>> zero -- crashing the kernel during modprobe of amdgpu on an RX 9070 XT.
> 
> Mhm in general not a bad idea, but we are having tons of GFX 12 systems in our test machines and nothing is crashing there.
> 
> We are clearly missing something here. Is that on an upstream kernel or something backported?
> 

the reported oops/etc say 6.18.22 so that does not sound like something crazy backported

(https://bugzilla.kernel.org/show_bug.cgi?id=221376)