[PATCH] drm/amdgpu: fix max_entries calculation

[Christian König]

Am 02.09.20 um 15:02 schrieb Pan, Xinhui:
>
>> 2020年9月2日 20:05，Christian König <ckoenig.leichtzumerken at gmail.com> 写道：
>>
>> Calculate the correct value for max_entries or we might run after the
>> page_address array.
>>
>> Signed-off-by: Christian König <christian.koenig at amd.com>
>> Fixes: 1e691e244487 drm/amdgpu: stop allocating dummy GTT nodes
>> ---
>> drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> index 8bc2253939be..8aa9584c184f 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> @@ -1697,7 +1697,8 @@ static int amdgpu_vm_bo_split_mapping(struct amdgpu_device *adev,
>> 				AMDGPU_GPU_PAGES_IN_CPU_PAGE;
>> 		} else {
>> 			addr = 0;
>> -			max_entries = S64_MAX;
>> +			max_entries = ((mapping->last - mapping->start) >>
>> +				       AMDGPU_GPU_PAGE_SHIFT) + 1;
> should it be like below?
> max_entries = (mapping->last - mapping->start + 1 - pfn) * AMDGPU_GPU_PAGES_IN_CPU_PAGE;

Still not correct, but mine wasn't correct either.

> last and start are already pfns. why still >> AMDGPU_GPU_PAGE_SHIFT? Am I missing something?

Yeah, that's wrong.

But this is in AMDGPU_GPU_PAGE_SIZE units and not PAGE_SIZE units, so 
multiplying it with AMDGPU_GPU_PAGES_IN_CPU_PAGE doesn't make to much 
sense either.

Christian.

>
>> 		}
>>
>> 		if (pages_addr) {
>> -- 
>> 2.17.1
>>