Re: [PATCH 04/11] drm/amdgpu: completely rework eviction fence handling

["Christian König" <christian.koenig@amd.com>]

On 3/17/26 12:21, Liang, Prike wrote:
> [Public]
> 
> Regards,
>       Prike
> 
>> -----Original Message-----
>> From: Koenig, Christian <Christian.Koenig@amd.com>
>> Sent: Tuesday, March 17, 2026 5:57 PM
>> To: Liang, Prike <Prike.Liang@amd.com>; tursulin@ursulin.net; Deucher, Alexander
>> <Alexander.Deucher@amd.com>; Mohan Marimuthu, Yogesh
>> <Yogesh.Mohanmarimuthu@amd.com>; SHANMUGAM, SRINIVASAN
>> <SRINIVASAN.SHANMUGAM@amd.com>; Khatri, Sunil <Sunil.Khatri@amd.com>;
>> amd-gfx@lists.freedesktop.org
>> Subject: Re: [PATCH 04/11] drm/amdgpu: completely rework eviction fence handling
>>
>> On 3/13/26 09:28, Liang, Prike wrote:
>>>> +void amdgpu_evf_mgr_attach_fence(struct amdgpu_eviction_fence_mgr
>> *evf_mgr,
>>>> +                              struct amdgpu_bo *bo) {
>>>> +     struct dma_fence *ev_fence = amdgpu_evf_mgr_get_fence(evf_mgr);
>>>> +     struct dma_resv *resv = bo->tbo.base.resv;
>>>
>>> Before adding the attached fence, there requires allocating the reservation fence
>> slot first.
>>
>> No, the caller does that using the drm_exec.
>>
>> Additional to that it is way to late to do any memory allocation here since that could
>> cycle back and wait for us to attach the eviction fence.
>>
>> So by reserving a slot here you would just create a potential deadlock.
> 
> Is possible pass the wrong fence number through the amdgpu_vm_lock_pd()/drm_exec_prepare_obj()? I saw the fence number assert error during attaching the reservation fence.

Yeah that is perfectly possible.

For kernel queues you need to have something like number_of_gang_members + 1 (for TTM) + 1 (for page table updates).

For user queues we probably need 1 (for TTM) + 1 (for page tables updates) + 1 (for the eviction fence).

Not sure if the calculation was really correct.

Regards,
Christian.

> 
>> Regards,
>> Christian.