[PATCH] drm/amdgpu: Restore uncache behaviour on GFX12

[Felix Kuehling]

On 2024-07-08 17:41, David Belanger wrote:
> Always use MTYPE_UC if UNCACHED flag is specified.
> 
> This makes kernarg region uncached and it restores
> usermode cache disable debug flag functionality.
> 
> Do not set MTYPE_UC for COHERENT flag, on GFX12 coherence is handled by
> shader code.
> 
> Signed-off-by: David Belanger <david.belanger at amd.com>

Reviewed-by: Felix Kuehling <felix.kuehling at amd.com>


> ---
>  drivers/gpu/drm/amd/amdgpu/gmc_v12_0.c | 21 ++-------------------
>  drivers/gpu/drm/amd/amdkfd/kfd_svm.c   |  8 +-------
>  2 files changed, 3 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v12_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v12_0.c
> index fd3ac483760e..542225eb13b5 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gmc_v12_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gmc_v12_0.c
> @@ -498,9 +498,6 @@ static void gmc_v12_0_get_vm_pte(struct amdgpu_device *adev,
>  				 uint64_t *flags)
>  {
>  	struct amdgpu_bo *bo = mapping->bo_va->base.bo;
> -	struct amdgpu_device *bo_adev;
> -	bool coherent, is_system;
> -
>  
>  	*flags &= ~AMDGPU_PTE_EXECUTABLE;
>  	*flags |= mapping->flags & AMDGPU_PTE_EXECUTABLE;
> @@ -516,25 +513,11 @@ static void gmc_v12_0_get_vm_pte(struct amdgpu_device *adev,
>  		*flags &= ~AMDGPU_PTE_VALID;
>  	}
>  
> -	if (!bo)
> -		return;
> -
> -	if (bo->flags & (AMDGPU_GEM_CREATE_COHERENT |
> -			       AMDGPU_GEM_CREATE_UNCACHED))
> -		*flags = AMDGPU_PTE_MTYPE_GFX12(*flags, MTYPE_UC);
> -
> -	bo_adev = amdgpu_ttm_adev(bo->tbo.bdev);
> -	coherent = bo->flags & AMDGPU_GEM_CREATE_COHERENT;
> -	is_system = (bo->tbo.resource->mem_type == TTM_PL_TT) ||
> -		(bo->tbo.resource->mem_type == AMDGPU_PL_PREEMPT);
> -
>  	if (bo && bo->flags & AMDGPU_GEM_CREATE_GFX12_DCC)
>  		*flags |= AMDGPU_PTE_DCC;
>  
> -	/* WA for HW bug */
> -	if (is_system || ((bo_adev != adev) && coherent))
> -		*flags = AMDGPU_PTE_MTYPE_GFX12(*flags, MTYPE_NC);
> -
> +	if (bo && bo->flags & AMDGPU_GEM_CREATE_UNCACHED)
> +		*flags = AMDGPU_PTE_MTYPE_GFX12(*flags, MTYPE_UC);
>  }
>  
>  static unsigned gmc_v12_0_get_vbios_fb_size(struct amdgpu_device *adev)
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> index bd9c2921e0dc..7b671aefab01 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> @@ -1248,13 +1248,7 @@ svm_range_get_pte_flags(struct kfd_node *node,
>  		break;
>  	case IP_VERSION(12, 0, 0):
>  	case IP_VERSION(12, 0, 1):
> -		if (domain == SVM_RANGE_VRAM_DOMAIN) {
> -			if (bo_node != node)
> -				mapping_flags |= AMDGPU_VM_MTYPE_NC;
> -		} else {
> -			mapping_flags |= coherent ?
> -				AMDGPU_VM_MTYPE_UC : AMDGPU_VM_MTYPE_NC;
> -		}
> +		mapping_flags |= AMDGPU_VM_MTYPE_NC;
>  		break;
>  	default:
>  		mapping_flags |= coherent ?