[PATCH v4 04/13] mm/migrate_device: Add migrate PFN flag to track device private pages

Jordan Niethe
2026-01-30T10:51:55Z

address space. This will mean that device private pages no longer have
normal PFN and must be handled separately.

Prepare for this by adding a MIGRATE_PFN_DEVICE_PRIVATE flag to indicate
that a migrate pfn contains a PFN for a device private page.

Acked-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Jordan Niethe <jniethe@nvidia.com>
Signed-off-by: Alistair Popple <apopple@nvidia.com>

---
v1:
- Update for HMM huge page support
- Update existing drivers to use MIGRATE_PFN_DEVICE
v2:
- Include changes to migrate_pfn_from_page()
- Rename to MIGRATE_PFN_DEVICE_PRIVATE
- drm/amd: Check adev->gmc.xgmi.connected_to_cpu
- lib/test_hmm.c: Check chunk->pagemap.type == MEMORY_DEVICE_PRIVATE

v3:
- Use adev->kfd.pgmap.type == MEMORY_DEVICE_PRIVATE

v4:
- No change
---
drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 7 ++++++-
drivers/gpu/drm/nouveau/nouveau_dmem.c | 3 ++-
drivers/gpu/drm/xe/xe_svm.c | 2 +-
include/linux/migrate.h | 14 +++++++++-----
lib/test_hmm.c | 6 +++++-
5 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
index 3dd7a35d19f7..5478e41877e5 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
@@ -212,7 +212,12 @@ svm_migrate_copy_done(struct amdgpu_device *adev, struct dma_fence *mfence)
unsigned long
svm_migrate_addr_to_mpfn(struct amdgpu_device *adev, unsigned long addr)
{
- return migrate_pfn((addr + adev->kfd.pgmap.range.start) >> PAGE_SHIFT);
+ unsigned long flags = 0;
+
+ if (adev->kfd.pgmap.type == MEMORY_DEVICE_PRIVATE)
+ flags |= MIGRATE_PFN_DEVICE_PRIVATE;
+ return migrate_pfn((addr + adev->kfd.pgmap.range.start) >> PAGE_SHIFT) |
+ flags;
}

static void
diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c b/drivers/gpu/drm/nouveau/nouveau_dmem.c
index bd3f7102c3f9..adfa3df5cbc5 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
@@ -484,7 +484,8 @@ nouveau_dmem_evict_chunk(struct nouveau_dmem_chunk *chunk)
dma_info = kvcalloc(npages, sizeof(*dma_info), GFP_KERNEL | __GFP_NOFAIL);

migrate_device_range(src_pfns,
- migrate_pfn(chunk->pagemap.range.start >> PAGE_SHIFT),
+ migrate_pfn(chunk->pagemap.range.start >> PAGE_SHIFT) |
+ MIGRATE_PFN_DEVICE_PRIVATE,
npages);

for (i = 0; i < npages; i++) {
diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c
index fbf5fd284616..a8aad9e0b1fb 100644
--- a/drivers/gpu/drm/xe/xe_svm.c
+++ b/drivers/gpu/drm/xe/xe_svm.c
@@ -770,7 +770,7 @@ static int xe_svm_populate_devmem_mpfn(struct drm_pagemap_devmem *devmem_allocat
int i;

for (i = 0; i < drm_buddy_block_size(buddy, block) >> PAGE_SHIFT; ++i)
- pfn[j++] = migrate_pfn(block_pfn + i);
+ pfn[j++] = migrate_pfn(block_pfn + i) | MIGRATE_PFN_DEVICE_PRIVATE;
}

return 0;
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index d269ec1400be..5fd2ee080bc0 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -122,11 +122,12 @@ static inline int migrate_misplaced_folio(struct folio *folio, int node)
* have enough bits to store all physical address and flags. So far we have
* enough room for all our flags.
*/
-#define MIGRATE_PFN_VALID (1UL << 0)
-#define MIGRATE_PFN_MIGRATE (1UL << 1)
-#define MIGRATE_PFN_WRITE (1UL << 3)
-#define MIGRATE_PFN_COMPOUND (1UL << 4)
-#define MIGRATE_PFN_SHIFT 6
+#define MIGRATE_PFN_VALID (1UL << 0)
+#define MIGRATE_PFN_MIGRATE (1UL << 1)
+#define MIGRATE_PFN_WRITE (1UL << 3)
+#define MIGRATE_PFN_COMPOUND (1UL << 4)
+#define MIGRATE_PFN_DEVICE_PRIVATE (1UL << 5)
+#define MIGRATE_PFN_SHIFT 6

static inline struct page *migrate_pfn_to_page(unsigned long mpfn)
{
@@ -142,6 +143,9 @@ static inline unsigned long migrate_pfn(unsigned long pfn)

static inline unsigned long migrate_pfn_from_page(struct page *page)
{
+ if (is_device_private_page(page))
+ return migrate_pfn(page_to_pfn(page)) |
+ MIGRATE_PFN_DEVICE_PRIVATE;
return migrate_pfn(page_to_pfn(page));
}

diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index a6ff292596f3..872d3846af7b 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -1385,11 +1385,15 @@ static void dmirror_device_evict_chunk(struct dmirror_chunk *chunk)
unsigned long *src_pfns;
unsigned long *dst_pfns;
unsigned int order = 0;
+ unsigned long flags = 0;

src_pfns = kvcalloc(npages, sizeof(*src_pfns), GFP_KERNEL | __GFP_NOFAIL);
dst_pfns = kvcalloc(npages, sizeof(*dst_pfns), GFP_KERNEL | __GFP_NOFAIL);

- migrate_device_range(src_pfns, migrate_pfn(start_pfn), npages);
+ if (chunk->pagemap.type == MEMORY_DEVICE_PRIVATE)
+ flags |= MIGRATE_PFN_DEVICE_PRIVATE;
+
+ migrate_device_range(src_pfns, migrate_pfn(start_pfn) | flags, npages);
for (i = 0; i < npages; i++) {
struct page *dpage, *spage;

--
2.34.1