[PATCH 5/7] drm/amdgpu: flush the HDP only once for CPU based VM updates

[Christian König]

Am 12.07.2017 um 22:31 schrieb Felix Kuehling:
> I'm wondering if you need a HDP flush in update_directories at all. Are
> there cases where the directories are updated but the page tables are not?

It can happen that a page table is swapped out and back in. In this case 
on the PDs need an update, but not the table itself.

Rather unlikely, but still possible.

> Also, in case of amdgpu_cs, I think we already have an HPD flush anyway.
> For KFD we don't use kernel-based submission, so we'd have to add an HDP
> flush into the KFD-specific VM mapping code.

Yeah, good point. But during CS the HDP flush comes after the VM flush.

I think we could change that, but I'm not 100% sure what the 
interactions with SRVIO are.

Christian.

>
> Either way, this is Reviewed-by: Felix Kuehling <Felix.Kuehling at amd.com>
>
> Regards,
>    Felix
>
>
> On 17-07-12 04:31 AM, Christian König wrote:
>> From: Christian König <christian.koenig at amd.com>
>>
>> No need to do this after every single update.
>>
>> Signed-off-by: Christian König <christian.koenig at amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 16 ++++++++++++----
>>   1 file changed, 12 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> index f52a358..1c6018b 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> @@ -991,10 +991,6 @@ static void amdgpu_vm_cpu_set_ptes(struct amdgpu_pte_update_params *params,
>>   					i, value, flags);
>>   		addr += incr;
>>   	}
>> -
>> -	/* Flush HDP */
>> -	mb();
>> -	amdgpu_gart_flush_gpu_tlb(params->adev, 0);
>>   }
>>   
>>   static int amdgpu_vm_wait_pd(struct amdgpu_device *adev, struct amdgpu_vm *vm,
>> @@ -1237,6 +1233,12 @@ int amdgpu_vm_update_directories(struct amdgpu_device *adev,
>>   	if (r)
>>   		amdgpu_vm_invalidate_level(&vm->root);
>>   
>> +	if (vm->use_cpu_for_update) {
>> +		/* Flush HDP */
>> +		mb();
>> +		amdgpu_gart_flush_gpu_tlb(adev, 0);
>> +	}
>> +
>>   	return r;
>>   }
>>   
>> @@ -1745,6 +1747,12 @@ int amdgpu_vm_bo_update(struct amdgpu_device *adev,
>>   		list_add(&bo_va->vm_status, &vm->cleared);
>>   	spin_unlock(&vm->status_lock);
>>   
>> +	if (vm->use_cpu_for_update) {
>> +		/* Flush HDP */
>> +		mb();
>> +		amdgpu_gart_flush_gpu_tlb(adev, 0);
>> +	}
>> +
>>   	return 0;
>>   }
>>   
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