[PATCH] drm/amdgpu: Need to set moved to true when evict bo

[Zhang, Jerry (Junwei)]

On 08/29/2018 04:53 PM, Christian König wrote:
> Am 29.08.2018 um 04:52 schrieb Zhang, Jerry (Junwei):
>> On 08/28/2018 08:40 PM, Emily Deng wrote:
>>> Fix the VMC page fault when the running sequence is as below:
>>> 1.amdgpu_gem_create_ioctl
>>> 2.ttm_bo_swapout->amdgpu_vm_bo_invalidate, as not called
>>> amdgpu_vm_bo_base_init, so won't called
>>> list_add_tail(&base->bo_list, &bo->va). Even the bo was evicted,
>>> it won't set the bo_base->moved.
>>
>> IMO, the evicted bo should be created previously.
>> On BO creation we will add it to the bo->va as below:
>>
>> amdgpu_gem_create_ioctl
>>   drm_gem_handle_create
>>     amdgpu_gem_object_open
>
> And here is the problem. Between creating the BO and opening it in the client the BO can be evicted.

Thanks to explain that.

It's the key point, falling in Murphy's law as well.

Jerry

>
> That's what Emily's patch is handling here.
>
> Christian.
>
>> amdgpu_vm_bo_add
>>         amdgpu_vm_bo_base_init
>>           list_add_tail(&base->bo_list, &bo->va)
>>
>> Then it could be set moved in bo invalidate when evicting.
>>
>> could you provide a bit more backgroud about the issue?
>> looks a per vm bo is evicted and a new same bo created.
>>
>> Jerry
>>
>>> 3.drm_gem_open_ioctl->amdgpu_vm_bo_base_init, here only called
>>> list_move_tail(&base->vm_status, &vm->evicted), but not set the
>>> bo_base->moved.
>>> 4.amdgpu_vm_bo_map->amdgpu_vm_bo_insert_map, as the bo_base->moved is
>>> not set true, the function amdgpu_vm_bo_insert_map will call
>>> list_move(&bo_va->base.vm_status, &vm->moved)
>>> 5.amdgpu_cs_ioctl won't validate the swapout bo, as it is only in the
>>> moved list, not in the evict list. So VMC page fault occurs.
>>>
>>> Signed-off-by: Emily Deng <Emily.Deng at amd.com>
>>> ---
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 1 +
>>>   1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>> index 1f4b8df..015e20e 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>> @@ -172,6 +172,7 @@ static void amdgpu_vm_bo_base_init(struct amdgpu_vm_bo_base *base,
>>>        * is validated on next vm use to avoid fault.
>>>        * */
>>>       list_move_tail(&base->vm_status, &vm->evicted);
>>> +    base->moved = true;
>>>   }
>>>
>>>   /**
>>>
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