[PATCH 1/2] drm/amdgpu: free pasid early before converting a vm

[Das, Nirmoy]

On 6/23/2021 9:05 PM, Felix Kuehling wrote:
> On 2021-06-23 8:25 a.m., Nirmoy Das wrote:
>> VM code should not be responsible for freeing pasid as pasid
>> gets allocated outside of VM code, before initializing a vm.
>>
>> Signed-off-by: Nirmoy Das <nirmoy.das at amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 6 ++++++
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c           | 5 -----
>>   2 files changed, 6 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
>> index f96598279593..42e22b1fdfee 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
>> @@ -1287,6 +1287,12 @@ int 
>> amdgpu_amdkfd_gpuvm_acquire_process_vm(struct kgd_dev *kgd,
>>       if (avm->process_info)
>>           return -EINVAL;
>>   +    /* Free the original amdgpu allocated pasid,
>> +     * will be replaced with kfd allocated pasid
>> +     */
>> +    if (avm->pasid)
>> +        amdgpu_pasid_free(avm->pasid);
>> +
>
> If amdgpu_vm_make_compute fails, amdgpu_driver_postclose_kms will try 
> to free the PASID a second time because vm->pasid still points to it. 
> You could fix that by moving the amdgpu_pasid_free after a successful 
> amdgpu_vm_make_compute call. But that still means you're making an 
> assumption about the side effect of amdgpu_vm_make_compute on 
> vm->pasid. IMHO, splitting the amdgpu_pasid_free and the vm->pasid = 0 
> into two different functions is a mistake.


Makes sense, I think I can export amdgpu_vm_set_pasid() and then keep 
amdgpu_pasid_free and the vm->pasid = 0 together.


Regards,

Nirmoy

>
> Regards,
>   Felix
>
>
>>       /* Convert VM into a compute VM */
>>       ret = amdgpu_vm_make_compute(adev, avm, pasid);
>>       if (ret)
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> index 63975bda8e76..be841d62a1d4 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> @@ -3094,11 +3094,6 @@ int amdgpu_vm_make_compute(struct 
>> amdgpu_device *adev, struct amdgpu_vm *vm,
>>           spin_lock_irqsave(&adev->vm_manager.pasid_lock, flags);
>>           idr_remove(&adev->vm_manager.pasid_idr, vm->pasid);
>> spin_unlock_irqrestore(&adev->vm_manager.pasid_lock, flags);
>> -
>> -        /* Free the original amdgpu allocated pasid
>> -         * Will be replaced with kfd allocated pasid
>> -         */
>> -        amdgpu_pasid_free(vm->pasid);
>>           vm->pasid = 0;
>>       }