Re: [PATCH v2 02/11] drm/amdkfd: Use migrate pfns internally

Felix Kuehling
2026-01-08T22:01:27Z

On 2026-01-07 04:18, 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() to 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@nvidia.com>
> ---
> v2:
> - New to series
> ---
> 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 ca552c34ece2..c493b19268cc 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> @@ -204,17 +204,17 @@ 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);
> @@ -225,7 +225,7 @@ 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);
> }
> @@ -235,7 +235,7 @@ 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);

I guess we rely on the fact that for DEVICE_PRIVATE memory,
adev->kfd.pgmap.range.start will be 0 after your patch 11. So we don't
need a special condition here to handle DEVICE_PRIVATE differently.

In general, I like the way you handle mpfns as it keeps all the special
casing out of the drivers.

Regards,
Felix

> }
>
> @@ -301,9 +301,8 @@ 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) */
>