linux-kernel - Re: [PATCH v3 02/13] drm/amdkfd: Use migrate pfns internally

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Message-ID: <5baa551b-98f6-4846-8279-db844dd701b2@nvidia.com>
Date: Wed, 28 Jan 2026 10:15:19 +1100
From: Balbir Singh <balbirs@...dia.com>
To: Jordan Niethe <jniethe@...dia.com>, linux-mm@...ck.org
Cc: matthew.brost@...el.com, akpm@...ux-foundation.org,
 linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 david@...hat.com, ziy@...dia.com, apopple@...dia.com,
 lorenzo.stoakes@...cle.com, lyude@...hat.com, dakr@...nel.org,
 airlied@...il.com, simona@...ll.ch, rcampbell@...dia.com,
 mpenttil@...hat.com, jgg@...dia.com, willy@...radead.org,
 linuxppc-dev@...ts.ozlabs.org, intel-xe@...ts.freedesktop.org, jgg@...pe.ca,
 Felix.Kuehling@....com, jhubbard@...dia.com
Subject: Re: [PATCH v3 02/13] drm/amdkfd: Use migrate pfns internally

On 1/23/26 17:22, Jordan Niethe wrote:
> A future change will remove device private pages from the physical
> address space. This will mean that device private pages no longer have a
> pfn.
> 
> A MIGRATE_PFN flag will be introduced that distinguishes between mpfns
> that contain a pfn vs an offset into device private memory.
> 
> Replace usages of pfns and page_to_pfn() with mpfns and
> migrate_pfn_to_page() to prepare for handling this distinction. This
> will assist in continuing to use the same code paths for both
> MEMORY_DEVICE_PRIVATE and MEMORY_DEVICE_COHERENT devices.
> 
> Signed-off-by: Jordan Niethe <jniethe@...dia.com>
> ---
> v2:
>   - New to series
> v3:
>   - No change
> ---
>  drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 15 +++++++--------
>  drivers/gpu/drm/amd/amdkfd/kfd_migrate.h |  2 +-
>  2 files changed, 8 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> index 1f03cf7342a5..3dd7a35d19f7 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> @@ -210,17 +210,17 @@ svm_migrate_copy_done(struct amdgpu_device *adev, struct dma_fence *mfence)
>  }
>  
>  unsigned long
> -svm_migrate_addr_to_pfn(struct amdgpu_device *adev, unsigned long addr)
> +svm_migrate_addr_to_mpfn(struct amdgpu_device *adev, unsigned long addr)
>  {
> -	return (addr + adev->kfd.pgmap.range.start) >> PAGE_SHIFT;
> +	return migrate_pfn((addr + adev->kfd.pgmap.range.start) >> PAGE_SHIFT);
>  }
>  
>  static void
> -svm_migrate_get_vram_page(struct svm_range *prange, unsigned long pfn)
> +svm_migrate_get_vram_page(struct svm_range *prange, unsigned long mpfn)
>  {
>  	struct page *page;
>  
> -	page = pfn_to_page(pfn);
> +	page = migrate_pfn_to_page(mpfn);
>  	svm_range_bo_ref(prange->svm_bo);
>  	page->zone_device_data = prange->svm_bo;
>  	zone_device_page_init(page, 0);
> @@ -231,7 +231,7 @@ svm_migrate_put_vram_page(struct amdgpu_device *adev, unsigned long addr)
>  {
>  	struct page *page;
>  
> -	page = pfn_to_page(svm_migrate_addr_to_pfn(adev, addr));
> +	page = migrate_pfn_to_page(svm_migrate_addr_to_mpfn(adev, addr));
>  	unlock_page(page);
>  	put_page(page);
>  }
> @@ -241,7 +241,7 @@ svm_migrate_addr(struct amdgpu_device *adev, struct page *page)
>  {
>  	unsigned long addr;
>  
> -	addr = page_to_pfn(page) << PAGE_SHIFT;
> +	addr = (migrate_pfn_from_page(page) >> MIGRATE_PFN_SHIFT) << PAGE_SHIFT;
>  	return (addr - adev->kfd.pgmap.range.start);
>  }
>  
> @@ -307,9 +307,8 @@ svm_migrate_copy_to_vram(struct kfd_node *node, struct svm_range *prange,
>  
>  		if (migrate->src[i] & MIGRATE_PFN_MIGRATE) {
>  			dst[i] = cursor.start + (j << PAGE_SHIFT);
> -			migrate->dst[i] = svm_migrate_addr_to_pfn(adev, dst[i]);
> +			migrate->dst[i] = svm_migrate_addr_to_mpfn(adev, dst[i]);
>  			svm_migrate_get_vram_page(prange, migrate->dst[i]);
> -			migrate->dst[i] = migrate_pfn(migrate->dst[i]);
>  			mpages++;
>  		}
>  		spage = migrate_pfn_to_page(migrate->src[i]);
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.h b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.h
> index 2b7fd442d29c..a80b72abe1e0 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.h
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.h
> @@ -48,7 +48,7 @@ int svm_migrate_vram_to_ram(struct svm_range *prange, struct mm_struct *mm,
>  			    uint32_t trigger, struct page *fault_page);
>  
>  unsigned long
> -svm_migrate_addr_to_pfn(struct amdgpu_device *adev, unsigned long addr);
> +svm_migrate_addr_to_mpfn(struct amdgpu_device *adev, unsigned long addr);
>  
>  #endif /* IS_ENABLED(CONFIG_HSA_AMD_SVM) */
>  

Looks good!
Acked-by: Balbir Singh <balbirs@...dia.com>