[PATCH 1/2] drm/amdgpu: Fix a bug on flag table_freed

[Christian König]

Am 30.05.21 um 20:29 schrieb Eric Huang:
>
> On 2021-05-30 12:54 p.m., Christian König wrote:
>>
>>
>> Am 30.05.21 um 00:51 schrieb Eric Huang:
>>> table_freed will be always true when mapping a memory with size
>>> bigger than 2MB. The problem is page table's entries are always
>>> existed, but existing mapping depends on page talbe's bo, so
>>> using a check of page table's bo existed will resolve the issue.
>>>
>>> Signed-off-by: Eric Huang <jinhuieric.huang at amd.com>
>>> ---
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 4 +++-
>>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c 
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>> index 0dee2e8797c7..95b94c95adac 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>> @@ -1582,9 +1582,11 @@ static int amdgpu_vm_update_ptes(struct 
>>> amdgpu_vm_update_params *params,
>>>                * completely covered by the range and so potentially 
>>> still in use.
>>>                */
>>>               while (cursor.pfn < frag_start) {
>>> +                /* Make sure previous mapping existed */
>>> +                if (cursor.entry->base.bo)
>>> +                    params->table_freed = true;
>>
>> In general this is the correct approach, but I would push that 
>> decision into the amdgpu_vm_free_pts() function.
>>
>>> amdgpu_vm_free_pts(adev, params->vm, &cursor);
>>
>> So that we have here something like
>>
>> params->table_freed |= amdgpu_vm_free_pts(..);
>>
> Thank you for your review. I was thinking put the check into function 
> amdgpu_vm_free_pts() since previous review, it will change returns of 
> two functions amdgpu_vm_free_pts() and amdgpu_vm_free_table(). If the 
> returns are not used by other functions, it seems make a simple change 
> complex from my perspective. Can you share the reason of your suggestion?

Because you can also optimize the bulk_moveable handling in that function.

E.g. bulk_moveable should only be set to false when a table was freed.

The only case where this doesn't matter is vm_fini and we really don't 
care for that special one.

Regards,
Christian.

>
> Regards,
> Eric
>>
>> Regards,
>> Christian.
>>
>>> amdgpu_vm_pt_next(adev, &cursor);
>>> -                params->table_freed = true;
>>>               }
>>>             } else if (frag >= shift) {
>>
>