> 2020年9月2日 22:31，Christian König <ckoenig.leichtzumerken@xxxxxxxxx> 写道：
>
> Am 02.09.20 um 16:27 schrieb Pan, Xinhui:
>>
>>> 2020年9月2日 22:05，Christian König <ckoenig.leichtzumerken@xxxxxxxxx> 写道：
>>>
>>> Calculate the correct value for max_entries or we might run after the
>>> page_address array.
>>>
>>> v2: Xinhui pointed out we don't need the shift
>>>
>>> Signed-off-by: Christian König <christian.koenig@xxxxxxx>
>>> Fixes: 1e691e244487 drm/amdgpu: stop allocating dummy GTT nodes
>>> ---
>>> drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>> index 8bc2253939be..be886bdca5c6 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>> @@ -1697,7 +1697,7 @@ 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 + 1;
>> You need minus pfn here.
>
> That doesn't sound correct either. The pfn is the destination of the mapping, e.g. the offset inside the BO and not related to the virtual address range we map.
I mean we need minus pfn too. pfn is mapping->offset >> PAGE_SHIFT.
In amdgpu_vm_bo_map(), there is a check below
if (bo && offset + size > amdgpu_bo_size(bo))
return -EINVAL;
so mapping->offset is just an offset_in_bytes inside the BO as you said.
mapping->start and mapping->last are virtual addresses in pfns, the range we are going to touch then is [start+ offset_in_pfns, last].
>
>> The range we are going to touch is [start + offset, last].
>> so the max_entries is last - (start + offset) + 1. and offset is pfn in this case.
>>
>> I still hit panic with this patch in practice.
>
> Thanks for testing, I think I know what the problem is.
>
> We need to start instead of mapping->start or otherwise the values is to large after the first iteration.
>
> Give me a second for a v3.
>
> Christian.
>
>>
>>> }
>>>
>>> if (pages_addr) {
>>> --
>>> 2.17.1
>>>
>
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