Re: [PATCH 1/2] drm/amdgpu: add amdgpu_vm_entries_mask

["Christian König" <ckoenig.leichtzumerken-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Am 17.09.2018 um 10:52 schrieb Huang Rui:
> On Sat, Sep 15, 2018 at 10:05:40AM +0200, Christian König wrote:
>> We can't get the mask for the root directory from the number of entries.
>>
>> So add a new function to avoid that problem.
>>
>> Signed-off-by: Christian König <christian.koenig@amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 34 +++++++++++++++++++++++++++-------
>>   1 file changed, 27 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> index a7f9aaa47c49..aaf54fc8cafe 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> @@ -190,6 +190,26 @@ static unsigned amdgpu_vm_num_entries(struct amdgpu_device *adev,
>>   		return AMDGPU_VM_PTE_COUNT(adev);
>>   }
>>   
>> +/**
>> + * amdgpu_vm_entries_mask - the mask to get the entry number of a PD/PT
>> + *
>> + * @adev: amdgpu_device pointer
>> + * @level: VMPT level
>> + *
>> + * Returns:
>> + * The mask to extract the entry number of a PD/PT from an address.
>> + */
>> +static uint32_t amdgpu_vm_entries_mask(struct amdgpu_device *adev,
>> +				       unsigned int level)
>> +{
>> +	if (level <= adev->vm_manager.root_level)
>> +		return 0xffffffff;
>> +	else if (level != AMDGPU_VM_PTB)
>> +		return 0x1f;
> I think the mask should be 0x1ff (9 bits) while the level is on PDB. The
> purpose here is to figure out the PTE entry id with the mask, am I right.
> So the mask should bit width of one entry.

Oh, yes of course that is a typo.

Thanks for catching,
Christian.

>
> Thanks,
> Ray
>
>> +	else
>> +		return AMDGPU_VM_PTE_COUNT(adev) - 1;
>> +}
>> +
>>   /**
>>    * amdgpu_vm_bo_size - returns the size of the BOs in bytes
>>    *
>> @@ -399,17 +419,17 @@ static void amdgpu_vm_pt_start(struct amdgpu_device *adev,
>>   static bool amdgpu_vm_pt_descendant(struct amdgpu_device *adev,
>>   				    struct amdgpu_vm_pt_cursor *cursor)
>>   {
>> -	unsigned num_entries, shift, idx;
>> +	unsigned mask, shift, idx;
>>   
>>   	if (!cursor->entry->entries)
>>   		return false;
>>   
>>   	BUG_ON(!cursor->entry->base.bo);
>> -	num_entries = amdgpu_vm_num_entries(adev, cursor->level);
>> +	mask = amdgpu_vm_entries_mask(adev, cursor->level);
>>   	shift = amdgpu_vm_level_shift(adev, cursor->level);
>>   
>>   	++cursor->level;
>> -	idx = (cursor->pfn >> shift) % num_entries;
>> +	idx = (cursor->pfn >> shift) & mask;
>>   	cursor->parent = cursor->entry;
>>   	cursor->entry = &cursor->entry->entries[idx];
>>   	return true;
>> @@ -1599,7 +1619,7 @@ static int amdgpu_vm_update_ptes(struct amdgpu_pte_update_params *params,
>>   	amdgpu_vm_pt_start(adev, params->vm, start, &cursor);
>>   	while (cursor.pfn < end) {
>>   		struct amdgpu_bo *pt = cursor.entry->base.bo;
>> -		unsigned shift, parent_shift, num_entries;
>> +		unsigned shift, parent_shift, mask;
>>   		uint64_t incr, entry_end, pe_start;
>>   
>>   		if (!pt)
>> @@ -1654,9 +1674,9 @@ static int amdgpu_vm_update_ptes(struct amdgpu_pte_update_params *params,
>>   
>>   		/* Looks good so far, calculate parameters for the update */
>>   		incr = AMDGPU_GPU_PAGE_SIZE << shift;
>> -		num_entries = amdgpu_vm_num_entries(adev, cursor.level);
>> -		pe_start = ((cursor.pfn >> shift) & (num_entries - 1)) * 8;
>> -		entry_end = num_entries << shift;
>> +		mask = amdgpu_vm_entries_mask(adev, cursor.level);
>> +		pe_start = ((cursor.pfn >> shift) & mask) * 8;
>> +		entry_end = (mask + 1) << shift;
>>   		entry_end += cursor.pfn & ~(entry_end - 1);
>>   		entry_end = min(entry_end, end);
>>   
>> -- 
>> 2.14.1
>>
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