[Public]
>-----Original Message-----
>From: amd-gfx <[email protected]> On Behalf Of Lazar,
>Lijo
>Sent: Monday, October 13, 2025 12:39 PM
>To: Zhang, Jesse(Jie) <[email protected]>; amd-
>[email protected]; [email protected]
>Cc: Deucher, Alexander <[email protected]>; Koenig, Christian
><[email protected]>; Yang, Philip <[email protected]>
>Subject: RE: [PATCH] drm/ttm: Add NULL check in
>ttm_resource_manager_usage
>
>[AMD Official Use Only - AMD Internal Distribution Only]
>
>>-----Original Message-----
>>From: Zhang, Jesse(Jie) <[email protected]>
>>Sent: Monday, October 13, 2025 11:25 AM
>>To: Lazar, Lijo <[email protected]>; [email protected];
>>dri- [email protected]
>>Cc: Deucher, Alexander <[email protected]>; Koenig, Christian
>><[email protected]>; Yang, Philip <[email protected]>
>>Subject: RE: [PATCH] drm/ttm: Add NULL check in
>>ttm_resource_manager_usage
>>
>>[AMD Official Use Only - AMD Internal Distribution Only]
>>
>>> -----Original Message-----
>>> From: Lazar, Lijo <[email protected]>
>>> Sent: Monday, October 13, 2025 12:37 PM
>>> To: Zhang, Jesse(Jie) <[email protected]>;
>>> [email protected]; [email protected]
>>> Cc: Deucher, Alexander <[email protected]>; Koenig, Christian
>>> <[email protected]>; Zhang, Jesse(Jie) <[email protected]>;
>>> Yang, Philip <[email protected]>; Zhang, Jesse(Jie)
>>> <[email protected]>
>>> Subject: RE: [PATCH] drm/ttm: Add NULL check in
>>> ttm_resource_manager_usage
>>>
>>> [AMD Official Use Only - AMD Internal Distribution Only]
>>>
>>> The specific issue of trace with amdgpu_mem_info_vram_used_show
>>> should be fixed with this one - "drm/amdgpu: hide VRAM sysfs
>>> attributes on GPUs without VRAM"
>>Thanks @Lazar, Lijo, maybe we still can use this patch to fix this
>>crash when calling AMDGPU_CS and query AMDGPU_INFO_VRAM_USAGE.
>>or add check like the previous patch.
>>
>[lijo]
>
>Agree, there are indeed multiple places of ttm_resource_manager_usage call.
>You may follow the same check as in the hide VRAM patch -
>ttm_resource_manager_used - in case ttm doesn't take this change.
>
On a second look,
struct amdgpu_vram_mgr {
struct ttm_resource_manager manager;
Hence this won't work for something like this -
case AMDGPU_INFO_VRAM_USAGE:
ui64 = ttm_resource_manager_usage(&adev->mman.vram_mgr.manager);
Thanks,
Lijo
>Thanks,
>Lijo
>
>>Regards
>>Jesse
>>
>>[ 911.954646] BUG: kernel NULL pointer dereference, address:
>>00000000000008f8 [ 911.962437]
>>#PF: supervisor write access in kernel mode [ 912.007045] RIP:
>>0010:_raw_spin_lock+0x1e/0x40 [ 912.105151]
>>amdttm_resource_manager_usage+0x1f/0x40
>> [amdttm] [ 912.111579] amdgpu_cs_parser_bos.isra.0+0x543/0x800
>>[amdgpu]
>>
>>>
>>> Thanks,
>>> Lijo
>>> >-----Original Message-----
>>> >From: amd-gfx <[email protected]> On Behalf Of
>>> >Jesse.Zhang
>>> >Sent: Monday, October 13, 2025 7:25 AM
>>> >To: [email protected]; [email protected]
>>> >Cc: Deucher, Alexander <[email protected]>; Koenig,
>>> >Christian <[email protected]>; Zhang, Jesse(Jie)
>>> ><[email protected]>; Yang, Philip <[email protected]>; Zhang,
>>> >Jesse(Jie) <[email protected]>
>>> >Subject: [PATCH] drm/ttm: Add NULL check in
>>> >ttm_resource_manager_usage
>>> >
>>> >Add a NULL pointer check in ttm_resource_manager_usage() to prevent
>>> >kernel NULL pointer dereferences when the function is called with an
>>> >uninitialized resource manager.
>>> >
>>> >This fixes a kernel OOPS observed on APU devices where the VRAM
>>> >resource manager is not fully initialized, but various sysfs and
>>> >debug interfaces still attempt to query VRAM usage statistics.
>>> >
>>> >The crash backtrace showed:
>>> > BUG: kernel NULL pointer dereference, address: 00000000000008f8
>>> > Call Trace:
>>> > amdttm_resource_manager_usage+0x1f/0x40 [amdttm]
>>> > amdgpu_mem_info_vram_used_show+0x1e/0x40 [amdgpu]
>>> > dev_attr_show+0x1d/0x40
>>> > kernfs_seq_show+0x27/0x30
>>> >
>>> >By returning 0 for NULL managers, we allow callers to safely query
>>> >usage information even when the underlying resource manager is not
>>> >available, which is the expected behavior for devices without
>>> >dedicated VRAM like
>>> APUs.
>>> >
>>> >Suggested-by: Philip Yang <[email protected]>
>>> >Signed-off-by: Jesse Zhang <[email protected]>
>>> >---
>>> > drivers/gpu/drm/ttm/ttm_resource.c | 3 +++
>>> > 1 file changed, 3 insertions(+)
>>> >
>>> >diff --git a/drivers/gpu/drm/ttm/ttm_resource.c
>>> >b/drivers/gpu/drm/ttm/ttm_resource.c
>>> >index e2c82ad07eb4..e4d45f75e40a 100644
>>> >--- a/drivers/gpu/drm/ttm/ttm_resource.c
>>> >+++ b/drivers/gpu/drm/ttm/ttm_resource.c
>>> >@@ -587,6 +587,9 @@ uint64_t ttm_resource_manager_usage(struct
>>> >ttm_resource_manager *man) {
>>> > uint64_t usage;
>>> >
>>> >+ if (!man)
>>> >+ return 0;
>>> >+
>>> > spin_lock(&man->bdev->lru_lock);
>>> > usage = man->usage;
>>> > spin_unlock(&man->bdev->lru_lock);
>>> >--
>>> >2.49.0
>>>
>>
