Re: [PATCH v7 1/6] drm/amdgpu: Fix init ordering in amdgpu_vram_mgr_init()

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Hey,

Can I merge this through drm-misc-next together with the rest of the series?

Kind regards
~Maarten

On 7/7/26 20:05, Arunpravin Paneer Selvam wrote:
> 
> 
> On 7/3/2026 6:38 PM, Christian König wrote:
>> Arun please take a look at this.
> Sure Christian. This fix looks correct to me.
> Reviewed-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
> 
> Thanks,
> Arun.
>>
>> Thanks,
>> Christian.
>>
>> On 7/3/26 15:05, Thomas Hellström wrote:
>>> drmm_cgroup_register_region() is called before INIT_LIST_HEAD() and
>>> gpu_buddy_init() in amdgpu_vram_mgr_init(). If it fails, the function
>>> returns early and bypasses those initializations.
>>>
>>> Since adev->mman.initialized is set to true before amdgpu_vram_mgr_init()
>>> is called, a failure triggers amdgpu_ttm_fini(), which calls
>>> amdgpu_vram_mgr_fini(), which then:
>>>
>>>   - Calls list_for_each_entry_safe() on reservations_pending and
>>>     reserved_pages, whose list_head::next pointers are zero-initialized
>>>     (NULL). The loop does not recognize them as empty and dereferences NULL.
>>>
>>>   - Calls gpu_buddy_fini(), which iterates free_trees[] unconditionally
>>>     via for_each_free_tree(). Since mm->free_trees is NULL
>>>     (never allocated), this dereferences NULL.
>>>
>>> Both result in a kernel panic on the module load error path.
>>>
>>> Fix by moving drmm_cgroup_register_region() to after the list and buddy
>>> allocator are fully initialized, so the teardown path is safe to run.
>>>
>>> Reported-by: Sashiko-bot <sashiko-bot@kernel.org>
>>> Closes: https://sashiko.dev/#/patchset/20260428073116.15687-1-thomas.hellstrom@linux.intel.com?part=4
>>> Fixes: 2b624a2c1865 ("drm/ttm: Handle cgroup based eviction in TTM")
>>> Cc: Friedrich Vock <friedrich.vock@gmx.de>
>>> Cc: Maarten Lankhorst <dev@lankhorst.se>
>>> Cc: Tejun Heo <tj@kernel.org>
>>> Cc: Maxime Ripard <mripard@kernel.org>
>>> Cc: Christian König <christian.koenig@amd.com>
>>> Cc: Alex Deucher <alexander.deucher@amd.com>
>>> Cc: amd-gfx@lists.freedesktop.org
>>> Cc: dri-devel@lists.freedesktop.org
>>> Cc: <stable@vger.kernel.org> # v6.14+
>>> Assisted-by: GitHub_Copilot:claude-sonnet-4.6
>>> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>>> ---
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 7 ++++---
>>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>>> index 2a241a5b12c4..ac3f71d77140 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>>> @@ -918,9 +918,6 @@ int amdgpu_vram_mgr_init(struct amdgpu_device *adev)
>>>       struct ttm_resource_manager *man = &mgr->manager;
>>>       int err;
>>>   -    man->cg = drmm_cgroup_register_region(adev_to_drm(adev), "vram", adev->gmc.real_vram_size);
>>> -    if (IS_ERR(man->cg))
>>> -        return PTR_ERR(man->cg);
>>>       ttm_resource_manager_init(man, &adev->mman.bdev,
>>>                     adev->gmc.real_vram_size);
>>>   @@ -935,6 +932,10 @@ int amdgpu_vram_mgr_init(struct amdgpu_device *adev)
>>>       if (err)
>>>           return err;
>>>   +    man->cg = drmm_cgroup_register_region(adev_to_drm(adev), "vram", adev->gmc.real_vram_size);
>>> +    if (IS_ERR(man->cg))
>>> +        return PTR_ERR(man->cg);
>>> +
>>>       ttm_set_driver_manager(&adev->mman.bdev, TTM_PL_VRAM, &mgr->manager);
>>>       ttm_resource_manager_set_used(man, true);
>>>       return 0;
>