Re: [PATCH 1/7] drm/amdgpu: fix VM PD addr shift

[Chunming Zhou <zhoucm1-5C7GfCeVMHo@public.gmane.org>]

On 2017年11月28日 00:02, Christian König wrote:
> The block size only affects the leave nodes, everything else is fixed.
This is not true, block size affects every level entries, see the 
register explains for VM_CONTEXTx_CNTL.PAGE_TABLE_BLOCK_SIZE:
"LOG2(number of 2MB logical address ranges) pointed to by a PDE0 page 
text directory entry. The native page size for the component ptes comes 
from the PDE0.block_fragment_size field or BASE_ADDR.block_fragment_size 
field (for a flat page table). The PAGE_TABLE_BLOCK_SIZE field only has 
an effect on address calculations for >= 2 level page tables however. A 
flat page table will utilize as many ptes as are required to represent 
the logical address between START_ADDR and END_ADDR, not limited by 
PAGE_TABLE_BLOCK_SIZE."

Regards,
David Zhou
>
> Signed-off-by: Christian König <christian.koenig@amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 28 +++++++++++++++++++++++-----
>   1 file changed, 23 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> index 122379dfc7d8..f1e541e9b514 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -139,6 +139,24 @@ struct amdgpu_prt_cb {
>   };
>   
>   /**
> + * amdgpu_vm_level_shift - return the addr shift for each level
> + *
> + * @adev: amdgpu_device pointer
> + *
> + * Returns the number of bits the pfn needs to be right shifted for a level.
> + */
> +static unsigned amdgpu_vm_level_shift(struct amdgpu_device *adev,
> +				      unsigned level)
> +{
> +	if (level != adev->vm_manager.num_level)
> +		return 9 * (adev->vm_manager.num_level - level - 1) +
> +			adev->vm_manager.block_size;
> +	else
> +		/* For the page tables on the leaves */
> +		return 0;
> +}
> +
> +/**
>    * amdgpu_vm_num_entries - return the number of entries in a PD/PT
>    *
>    * @adev: amdgpu_device pointer
> @@ -288,8 +306,7 @@ static int amdgpu_vm_alloc_levels(struct amdgpu_device *adev,
>   				  uint64_t saddr, uint64_t eaddr,
>   				  unsigned level)
>   {
> -	unsigned shift = (adev->vm_manager.num_level - level) *
> -		adev->vm_manager.block_size;
> +	unsigned shift = amdgpu_vm_level_shift(adev, level);
>   	unsigned pt_idx, from, to;
>   	int r;
>   	u64 flags;
> @@ -1302,18 +1319,19 @@ void amdgpu_vm_get_entry(struct amdgpu_pte_update_params *p, uint64_t addr,
>   			 struct amdgpu_vm_pt **entry,
>   			 struct amdgpu_vm_pt **parent)
>   {
> -	unsigned idx, level = p->adev->vm_manager.num_level;
> +	unsigned level = 0;
>   
>   	*parent = NULL;
>   	*entry = &p->vm->root;
>   	while ((*entry)->entries) {
> -		idx = addr >> (p->adev->vm_manager.block_size * level--);
> +		unsigned idx = addr >> amdgpu_vm_level_shift(p->adev, level++);
> +
>   		idx %= amdgpu_bo_size((*entry)->base.bo) / 8;
>   		*parent = *entry;
>   		*entry = &(*entry)->entries[idx];
>   	}
>   
> -	if (level)
> +	if (level != p->adev->vm_manager.num_level)
>   		*entry = NULL;
>   }
>   

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