[PATCH v2] drm/amdkfd: simplify vm_validate_pt_pd_bos

[Christian König]

Am 13.06.22 um 10:41 schrieb Lang Yu:
> On 06/13/ , Christian König wrote:
>> Am 13.06.22 um 10:26 schrieb Lang Yu:
>>> On 06/13/ , Christian König wrote:
>>>> Am 13.06.22 um 09:59 schrieb Lang Yu:
>>>>> We don't need to validate and map root PD specially here,
>>>>> it would be validated and mapped by amdgpu_vm_validate_pt_bos
>>>>> if it is evicted.
>>>> I'm not sure if that's correct. Traditionally we have handled the root PD
>>>> differently to the rest in the VM.
>>>>
>>>> It doesn't make much sense any more today, but I need to double check if
>>>> that isn't still the case.
>>>   From my observations, if root PD is evicted. amdgpu_vm_validate_pt_bos
>>> will validate and map it.
>>>
>>> And amdgpu_cs_list_validate always validates root PD after
>>> amdgpu_vm_validate_pt_bos has done that, it is actually unnecessary.
>>> Do you think it's worth skiping root PD validation in
>>> amdgpu_cs_list_validate? Thanks!
>> No, it's just your change is completely irrelevant and just complicates
>> things.
>>
>> Validating a BO twice should have basically no overhead at all.
>>
>> And especially adding the manual call to map_table() in
>> amdgpu_vm_make_compute() is a no-go. We don't want such specific handling
>> for compute contexts.
> That's because when turning a GFX VM to a compute VM, if vm_update_mode changed,
> we need to map the root PD again.

Ah, ok that sounds valid. But please add a comment explaining this.

> If we always validate and map it in vm_validate_pt_pd_bos, that's so confused.

It's indeed not really clean, we shouldn't leak requirements like this 
outside of the VM code.

Regards,
Christian.

>
> Regards,
> Lang
>
>> Regards,
>> Christian.
>>
>>> Regards,
>>> Lang
>>>
>>>
>>>> Christian.
>>>>
>>>>> The special case is when turning a GFX VM to a compute VM,
>>>>> if vm_update_mode changed, we need to map the root PD again.
>>>>> So just move root PD mapping to amdgpu_vm_make_compute.
>>>>>
>>>>> v2:
>>>>>     - Don't rename vm_validate_pt_pd_bos and make it public.
>>>>>
>>>>> Signed-off-by: Lang Yu <Lang.Yu at amd.com>
>>>>> ---
>>>>>     drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 14 --------------
>>>>>     drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c           |  5 +++++
>>>>>     2 files changed, 5 insertions(+), 14 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
>>>>> index 6a3bd8b9a08f..3805eef9ab69 100644
>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
>>>>> @@ -425,22 +425,8 @@ static int vm_validate_pt_pd_bos(struct amdgpu_vm *vm)
>>>>>     		return ret;
>>>>>     	}
>>>>> -	ret = amdgpu_amdkfd_validate_vm_bo(NULL, pd);
>>>>> -	if (ret) {
>>>>> -		pr_err("failed to validate PD\n");
>>>>> -		return ret;
>>>>> -	}
>>>>> -
>>>>>     	vm->pd_phys_addr = amdgpu_gmc_pd_addr(vm->root.bo);
>>>>> -	if (vm->use_cpu_for_update) {
>>>>> -		ret = amdgpu_bo_kmap(pd, NULL);
>>>>> -		if (ret) {
>>>>> -			pr_err("failed to kmap PD, ret=%d\n", ret);
>>>>> -			return ret;
>>>>> -		}
>>>>> -	}
>>>>> -
>>>>>     	return 0;
>>>>>     }
>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>>>> index 703552f9a6d7..08fda57f5aa2 100644
>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>>>> @@ -2225,6 +2225,11 @@ int amdgpu_vm_make_compute(struct amdgpu_device *adev, struct amdgpu_vm *vm)
>>>>>     	} else {
>>>>>     		vm->update_funcs = &amdgpu_vm_sdma_funcs;
>>>>>     	}
>>>>> +
>>>>> +	r = vm->update_funcs->map_table(to_amdgpu_bo_vm(vm->root.bo));
>>>>> +	if (r)
>>>>> +		goto unreserve_bo;
>>>>> +
>>>>>     	dma_fence_put(vm->last_update);
>>>>>     	vm->last_update = NULL;
>>>>>     	vm->is_compute_context = true;