A future change will remove device private pages from the physical
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 flag to indicate
that a migrate pfn contains a PFN for a device private page.
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
---
arch/powerpc/kvm/book3s_hv_uvmem.c | 2 +-
drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 3 ++-
drivers/gpu/drm/drm_pagemap.c | 2 +-
drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +-
include/linux/migrate.h | 1 +
lib/test_hmm.c | 4 ++--
mm/migrate_device.c | 11 ++++++++---
7 files changed, 16 insertions(+), 9 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
index e5000bef90f2..dac5d6454920 100644
--- a/arch/powerpc/kvm/book3s_hv_uvmem.c
+++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
@@ -784,7 +784,7 @@ static int kvmppc_svm_page_in(struct vm_area_struct *vma,
}
}
- *mig.dst = migrate_pfn(page_to_pfn(dpage));
+ *mig.dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_DEVICE;
migrate_vma_pages(&mig);
out_finalize:
migrate_vma_finalize(&mig);
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
index af53e796ea1b..0257c6e7f680 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
@@ -303,7 +303,8 @@ svm_migrate_copy_to_vram(struct kfd_node *node, struct svm_range *prange,
dst[i] = cursor.start + (j << PAGE_SHIFT);
migrate->dst[i] = svm_migrate_addr_to_pfn(adev, dst[i]);
svm_migrate_get_vram_page(prange, migrate->dst[i]);
- migrate->dst[i] = migrate_pfn(migrate->dst[i]);
+ migrate->dst[i] = migrate_pfn(migrate->dst[i]) |
+ MIGRATE_PFN_DEVICE;
mpages++;
}
spage = migrate_pfn_to_page(migrate->src[i]);
diff --git a/drivers/gpu/drm/drm_pagemap.c b/drivers/gpu/drm/drm_pagemap.c
index 37d7cfbbb3e8..0c756d73419f 100644
--- a/drivers/gpu/drm/drm_pagemap.c
+++ b/drivers/gpu/drm/drm_pagemap.c
@@ -404,7 +404,7 @@ int drm_pagemap_migrate_to_devmem(struct drm_pagemap_devmem *devmem_allocation,
struct page *page = pfn_to_page(migrate.dst[i]);
pages[i] = page;
- migrate.dst[i] = migrate_pfn(migrate.dst[i]);
+ migrate.dst[i] = migrate_pfn(migrate.dst[i]) | MIGRATE_PFN_DEVICE;
drm_pagemap_get_devmem_page(page, zdd);
}
diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c b/drivers/gpu/drm/nouveau/nouveau_dmem.c
index 58071652679d..2bd80c6f5bcd 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
@@ -766,7 +766,7 @@ static unsigned long nouveau_dmem_migrate_copy_one(struct nouveau_drm *drm,
((paddr >> PAGE_SHIFT) << NVIF_VMM_PFNMAP_V0_ADDR_SHIFT);
if (src & MIGRATE_PFN_WRITE)
*pfn |= NVIF_VMM_PFNMAP_V0_W;
- mpfn = migrate_pfn(page_to_pfn(dpage));
+ mpfn = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_DEVICE;
if (folio_order(page_folio(dpage)))
mpfn |= MIGRATE_PFN_COMPOUND;
return mpfn;
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 26ca00c325d9..52f65cd5c932 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -126,6 +126,7 @@ static inline int migrate_misplaced_folio(struct folio *folio, int node)
#define MIGRATE_PFN_MIGRATE (1UL << 1)
#define MIGRATE_PFN_WRITE (1UL << 3)
#define MIGRATE_PFN_COMPOUND (1UL << 4)
+#define MIGRATE_PFN_DEVICE (1UL << 5)
#define MIGRATE_PFN_SHIFT 6
static inline struct page *migrate_pfn_to_page(unsigned long mpfn)
diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index 8af169d3873a..19681904a666 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -727,7 +727,7 @@ static void dmirror_migrate_alloc_and_copy(struct migrate_vma *args,
rpage = BACKING_PAGE(dpage);
rpage->zone_device_data = dmirror;
- *dst = migrate_pfn(page_to_pfn(dpage)) | write;
+ *dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_DEVICE | write;
src_page = pfn_to_page(spfn + i);
if (spage)
@@ -754,7 +754,7 @@ static void dmirror_migrate_alloc_and_copy(struct migrate_vma *args,
pr_debug("migrating from sys to dev pfn src: 0x%lx pfn dst: 0x%lx\n",
page_to_pfn(spage), page_to_pfn(dpage));
- *dst = migrate_pfn(page_to_pfn(dpage)) | write;
+ *dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_DEVICE | write;
if (is_large) {
int i;
diff --git a/mm/migrate_device.c b/mm/migrate_device.c
index 23379663b1e1..5d108ddf1a97 100644
--- a/mm/migrate_device.c
+++ b/mm/migrate_device.c
@@ -199,6 +199,7 @@ static int migrate_vma_collect_huge_pmd(pmd_t *pmdp, unsigned long start,
(migrate->flags & MIGRATE_VMA_SELECT_COMPOUND) &&
(IS_ALIGNED(start, HPAGE_PMD_SIZE) &&
IS_ALIGNED(end, HPAGE_PMD_SIZE))) {
+ unsigned long device_private = 0;
struct page_vma_mapped_walk pvmw = {
.ptl = ptl,
@@ -208,10 +209,13 @@ static int migrate_vma_collect_huge_pmd(pmd_t *pmdp, unsigned long start,
};
unsigned long pfn = page_to_pfn(folio_page(folio, 0));
+ if (folio_is_device_private(folio))
+ device_private = MIGRATE_PFN_DEVICE;
migrate->src[migrate->npages] = migrate_pfn(pfn) | write
| MIGRATE_PFN_MIGRATE
- | MIGRATE_PFN_COMPOUND;
+ | MIGRATE_PFN_COMPOUND
+ | device_private;
migrate->dst[migrate->npages++] = 0;
migrate->cpages++;
ret = set_pmd_migration_entry(&pvmw, folio_page(folio, 0));
@@ -329,7 +333,8 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
}
mpfn = migrate_pfn(page_to_pfn(page)) |
- MIGRATE_PFN_MIGRATE;
+ MIGRATE_PFN_MIGRATE |
+ MIGRATE_PFN_DEVICE;
if (softleaf_is_device_private_write(entry))
mpfn |= MIGRATE_PFN_WRITE;
} else {
@@ -1368,7 +1373,7 @@ static unsigned long migrate_device_pfn_lock(unsigned long pfn)
return 0;
}
- return migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
+ return migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE | MIGRATE_PFN_DEVICE;
}
/**
--
2.34.1On 2025-12-30 23:31, 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
> normal PFN and must be handled separately.
>
> Prepare for this by adding a MIGRATE_PFN_DEVICE flag to indicate
> that a migrate pfn contains a PFN for a device private page.
Thanks for doing this. Some comments inline regarding DEVICE_COHERENT
pages. I suspect this will have ripple effects on the rest of the patch
series, at least in patch 8, but I haven't looked at that in detail yet.
>
> 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
> ---
> arch/powerpc/kvm/book3s_hv_uvmem.c | 2 +-
> drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 3 ++-
> drivers/gpu/drm/drm_pagemap.c | 2 +-
> drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +-
> include/linux/migrate.h | 1 +
> lib/test_hmm.c | 4 ++--
> mm/migrate_device.c | 11 ++++++++---
> 7 files changed, 16 insertions(+), 9 deletions(-)
>
> diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
> index e5000bef90f2..dac5d6454920 100644
> --- a/arch/powerpc/kvm/book3s_hv_uvmem.c
> +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
> @@ -784,7 +784,7 @@ static int kvmppc_svm_page_in(struct vm_area_struct *vma,
> }
> }
>
> - *mig.dst = migrate_pfn(page_to_pfn(dpage));
> + *mig.dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_DEVICE;
> migrate_vma_pages(&mig);
> out_finalize:
> migrate_vma_finalize(&mig);
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> index af53e796ea1b..0257c6e7f680 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> @@ -303,7 +303,8 @@ svm_migrate_copy_to_vram(struct kfd_node *node, struct svm_range *prange,
> dst[i] = cursor.start + (j << PAGE_SHIFT);
> migrate->dst[i] = svm_migrate_addr_to_pfn(adev, dst[i]);
> svm_migrate_get_vram_page(prange, migrate->dst[i]);
> - migrate->dst[i] = migrate_pfn(migrate->dst[i]);
> + migrate->dst[i] = migrate_pfn(migrate->dst[i]) |
> + MIGRATE_PFN_DEVICE;
On some of our GPUs we use DEVICE_COHERENT pages. These are pages that
are coherently accessible by the CPU and peer devices in the system
physical address space. Therefore, this needs to be conditional. Maybe
add something like adev->kfd.migrate_pfn_flag that gets initialized
conditionally in kgd2kfd_init_zone_device. Then add ... |
adev->kfd.migrate_pfn_flag here.
> mpages++;
> }
> spage = migrate_pfn_to_page(migrate->src[i]);
> diff --git a/drivers/gpu/drm/drm_pagemap.c b/drivers/gpu/drm/drm_pagemap.c
> index 37d7cfbbb3e8..0c756d73419f 100644
> --- a/drivers/gpu/drm/drm_pagemap.c
> +++ b/drivers/gpu/drm/drm_pagemap.c
> @@ -404,7 +404,7 @@ int drm_pagemap_migrate_to_devmem(struct drm_pagemap_devmem *devmem_allocation,
> struct page *page = pfn_to_page(migrate.dst[i]);
>
> pages[i] = page;
> - migrate.dst[i] = migrate_pfn(migrate.dst[i]);
> + migrate.dst[i] = migrate_pfn(migrate.dst[i]) | MIGRATE_PFN_DEVICE;
> drm_pagemap_get_devmem_page(page, zdd);
> }
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c b/drivers/gpu/drm/nouveau/nouveau_dmem.c
> index 58071652679d..2bd80c6f5bcd 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
> @@ -766,7 +766,7 @@ static unsigned long nouveau_dmem_migrate_copy_one(struct nouveau_drm *drm,
> ((paddr >> PAGE_SHIFT) << NVIF_VMM_PFNMAP_V0_ADDR_SHIFT);
> if (src & MIGRATE_PFN_WRITE)
> *pfn |= NVIF_VMM_PFNMAP_V0_W;
> - mpfn = migrate_pfn(page_to_pfn(dpage));
> + mpfn = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_DEVICE;
> if (folio_order(page_folio(dpage)))
> mpfn |= MIGRATE_PFN_COMPOUND;
> return mpfn;
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index 26ca00c325d9..52f65cd5c932 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -126,6 +126,7 @@ static inline int migrate_misplaced_folio(struct folio *folio, int node)
> #define MIGRATE_PFN_MIGRATE (1UL << 1)
> #define MIGRATE_PFN_WRITE (1UL << 3)
> #define MIGRATE_PFN_COMPOUND (1UL << 4)
> +#define MIGRATE_PFN_DEVICE (1UL << 5)
> #define MIGRATE_PFN_SHIFT 6
>
> static inline struct page *migrate_pfn_to_page(unsigned long mpfn)
> diff --git a/lib/test_hmm.c b/lib/test_hmm.c
> index 8af169d3873a..19681904a666 100644
> --- a/lib/test_hmm.c
> +++ b/lib/test_hmm.c
> @@ -727,7 +727,7 @@ static void dmirror_migrate_alloc_and_copy(struct migrate_vma *args,
> rpage = BACKING_PAGE(dpage);
> rpage->zone_device_data = dmirror;
>
> - *dst = migrate_pfn(page_to_pfn(dpage)) | write;
> + *dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_DEVICE | write;
This needs to be conditional on dmirror->mdevice->zone_device_type.
> src_page = pfn_to_page(spfn + i);
>
> if (spage)
> @@ -754,7 +754,7 @@ static void dmirror_migrate_alloc_and_copy(struct migrate_vma *args,
> pr_debug("migrating from sys to dev pfn src: 0x%lx pfn dst: 0x%lx\n",
> page_to_pfn(spage), page_to_pfn(dpage));
>
> - *dst = migrate_pfn(page_to_pfn(dpage)) | write;
> + *dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_DEVICE | write;
Same here.
>
> if (is_large) {
> int i;
> diff --git a/mm/migrate_device.c b/mm/migrate_device.c
> index 23379663b1e1..5d108ddf1a97 100644
> --- a/mm/migrate_device.c
> +++ b/mm/migrate_device.c
> @@ -199,6 +199,7 @@ static int migrate_vma_collect_huge_pmd(pmd_t *pmdp, unsigned long start,
> (migrate->flags & MIGRATE_VMA_SELECT_COMPOUND) &&
> (IS_ALIGNED(start, HPAGE_PMD_SIZE) &&
> IS_ALIGNED(end, HPAGE_PMD_SIZE))) {
> + unsigned long device_private = 0;
>
> struct page_vma_mapped_walk pvmw = {
> .ptl = ptl,
> @@ -208,10 +209,13 @@ static int migrate_vma_collect_huge_pmd(pmd_t *pmdp, unsigned long start,
> };
>
> unsigned long pfn = page_to_pfn(folio_page(folio, 0));
> + if (folio_is_device_private(folio))
> + device_private = MIGRATE_PFN_DEVICE;
>
> migrate->src[migrate->npages] = migrate_pfn(pfn) | write
> | MIGRATE_PFN_MIGRATE
> - | MIGRATE_PFN_COMPOUND;
> + | MIGRATE_PFN_COMPOUND
> + | device_private;
> migrate->dst[migrate->npages++] = 0;
> migrate->cpages++;
> ret = set_pmd_migration_entry(&pvmw, folio_page(folio, 0));
> @@ -329,7 +333,8 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
> }
>
> mpfn = migrate_pfn(page_to_pfn(page)) |
> - MIGRATE_PFN_MIGRATE;
> + MIGRATE_PFN_MIGRATE |
> + MIGRATE_PFN_DEVICE;
I think this also needs to be conditional to distinguish DEVICE_COHERENT
pages.
> if (softleaf_is_device_private_write(entry))
> mpfn |= MIGRATE_PFN_WRITE;
> } else {
> @@ -1368,7 +1373,7 @@ static unsigned long migrate_device_pfn_lock(unsigned long pfn)
> return 0;
> }
>
> - return migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
> + return migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE | MIGRATE_PFN_DEVICE;
Same here.
Regards,
Felix
> }
>
> /**
Hi,
On 1/1/26 04:03, Kuehling, Felix wrote:
> On 2025-12-30 23:31, 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
>> normal PFN and must be handled separately.
>>
>> Prepare for this by adding a MIGRATE_PFN_DEVICE flag to indicate
>> that a migrate pfn contains a PFN for a device private page.
>
> Thanks for doing this. Some comments inline regarding DEVICE_COHERENT
> pages. I suspect this will have ripple effects on the rest of the patch
> series, at least in patch 8, but I haven't looked at that in detail yet.
Ah thanks - I missed that MEMORY_DEVICE_COHERENT and
MEMORY_DEVICE_PRIVATE were
sharing some code paths.
>
>
>>
>> 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
>> ---
>> arch/powerpc/kvm/book3s_hv_uvmem.c | 2 +-
>> drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 3 ++-
>> drivers/gpu/drm/drm_pagemap.c | 2 +-
>> drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +-
>> include/linux/migrate.h | 1 +
>> lib/test_hmm.c | 4 ++--
>> mm/migrate_device.c | 11 ++++++++---
>> 7 files changed, 16 insertions(+), 9 deletions(-)
>>
>> diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/
>> book3s_hv_uvmem.c
>> index e5000bef90f2..dac5d6454920 100644
>> --- a/arch/powerpc/kvm/book3s_hv_uvmem.c
>> +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
>> @@ -784,7 +784,7 @@ static int kvmppc_svm_page_in(struct
>> vm_area_struct *vma,
>> }
>> }
>> - *mig.dst = migrate_pfn(page_to_pfn(dpage));
>> + *mig.dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_DEVICE;
>> migrate_vma_pages(&mig);
>> out_finalize:
>> migrate_vma_finalize(&mig);
>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/
>> drm/amd/amdkfd/kfd_migrate.c
>> index af53e796ea1b..0257c6e7f680 100644
>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
>> @@ -303,7 +303,8 @@ svm_migrate_copy_to_vram(struct kfd_node *node,
>> struct svm_range *prange,
>> dst[i] = cursor.start + (j << PAGE_SHIFT);
>> migrate->dst[i] = svm_migrate_addr_to_pfn(adev, dst[i]);
>> svm_migrate_get_vram_page(prange, migrate->dst[i]);
>> - migrate->dst[i] = migrate_pfn(migrate->dst[i]);
>> + migrate->dst[i] = migrate_pfn(migrate->dst[i]) |
>> + MIGRATE_PFN_DEVICE;
>
> On some of our GPUs we use DEVICE_COHERENT pages. These are pages that
> are coherently accessible by the CPU and peer devices in the system
> physical address space. Therefore, this needs to be conditional. Maybe
> add something like adev->kfd.migrate_pfn_flag that gets initialized
> conditionally in kgd2kfd_init_zone_device. Then add ... | adev-
> >kfd.migrate_pfn_flag here.
>
>
>> mpages++;
>> }
>> spage = migrate_pfn_to_page(migrate->src[i]);
>> diff --git a/drivers/gpu/drm/drm_pagemap.c b/drivers/gpu/drm/
>> drm_pagemap.c
>> index 37d7cfbbb3e8..0c756d73419f 100644
>> --- a/drivers/gpu/drm/drm_pagemap.c
>> +++ b/drivers/gpu/drm/drm_pagemap.c
>> @@ -404,7 +404,7 @@ int drm_pagemap_migrate_to_devmem(struct
>> drm_pagemap_devmem *devmem_allocation,
>> struct page *page = pfn_to_page(migrate.dst[i]);
>> pages[i] = page;
>> - migrate.dst[i] = migrate_pfn(migrate.dst[i]);
>> + migrate.dst[i] = migrate_pfn(migrate.dst[i]) |
>> MIGRATE_PFN_DEVICE;
>> drm_pagemap_get_devmem_page(page, zdd);
>> }
>> diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c b/drivers/gpu/drm/
>> nouveau/nouveau_dmem.c
>> index 58071652679d..2bd80c6f5bcd 100644
>> --- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
>> +++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
>> @@ -766,7 +766,7 @@ static unsigned long
>> nouveau_dmem_migrate_copy_one(struct nouveau_drm *drm,
>> ((paddr >> PAGE_SHIFT) << NVIF_VMM_PFNMAP_V0_ADDR_SHIFT);
>> if (src & MIGRATE_PFN_WRITE)
>> *pfn |= NVIF_VMM_PFNMAP_V0_W;
>> - mpfn = migrate_pfn(page_to_pfn(dpage));
>> + mpfn = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_DEVICE;
>> if (folio_order(page_folio(dpage)))
>> mpfn |= MIGRATE_PFN_COMPOUND;
>> return mpfn;
>> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
>> index 26ca00c325d9..52f65cd5c932 100644
>> --- a/include/linux/migrate.h
>> +++ b/include/linux/migrate.h
>> @@ -126,6 +126,7 @@ static inline int migrate_misplaced_folio(struct
>> folio *folio, int node)
>> #define MIGRATE_PFN_MIGRATE (1UL << 1)
>> #define MIGRATE_PFN_WRITE (1UL << 3)
>> #define MIGRATE_PFN_COMPOUND (1UL << 4)
>> +#define MIGRATE_PFN_DEVICE (1UL << 5)
>> #define MIGRATE_PFN_SHIFT 6
>> static inline struct page *migrate_pfn_to_page(unsigned long mpfn)
>> diff --git a/lib/test_hmm.c b/lib/test_hmm.c
>> index 8af169d3873a..19681904a666 100644
>> --- a/lib/test_hmm.c
>> +++ b/lib/test_hmm.c
>> @@ -727,7 +727,7 @@ static void dmirror_migrate_alloc_and_copy(struct
>> migrate_vma *args,
>> rpage = BACKING_PAGE(dpage);
>> rpage->zone_device_data = dmirror;
>> - *dst = migrate_pfn(page_to_pfn(dpage)) | write;
>> + *dst = migrate_pfn(page_to_pfn(dpage)) |
>> MIGRATE_PFN_DEVICE | write;
>
> This needs to be conditional on dmirror->mdevice->zone_device_type.
Good catch.
>
>
>> src_page = pfn_to_page(spfn + i);
>> if (spage)
>> @@ -754,7 +754,7 @@ static void dmirror_migrate_alloc_and_copy(struct
>> migrate_vma *args,
>> pr_debug("migrating from sys to dev pfn src: 0x%lx pfn dst:
>> 0x%lx\n",
>> page_to_pfn(spage), page_to_pfn(dpage));
>> - *dst = migrate_pfn(page_to_pfn(dpage)) | write;
>> + *dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_DEVICE |
>> write;
>
> Same here.
Agree.
>
>
>> if (is_large) {
>> int i;
>> diff --git a/mm/migrate_device.c b/mm/migrate_device.c
>> index 23379663b1e1..5d108ddf1a97 100644
>> --- a/mm/migrate_device.c
>> +++ b/mm/migrate_device.c
>> @@ -199,6 +199,7 @@ static int migrate_vma_collect_huge_pmd(pmd_t
>> *pmdp, unsigned long start,
>> (migrate->flags & MIGRATE_VMA_SELECT_COMPOUND) &&
>> (IS_ALIGNED(start, HPAGE_PMD_SIZE) &&
>> IS_ALIGNED(end, HPAGE_PMD_SIZE))) {
>> + unsigned long device_private = 0;
>> struct page_vma_mapped_walk pvmw = {
>> .ptl = ptl,
>> @@ -208,10 +209,13 @@ static int migrate_vma_collect_huge_pmd(pmd_t
>> *pmdp, unsigned long start,
>> };
>> unsigned long pfn = page_to_pfn(folio_page(folio, 0));
>> + if (folio_is_device_private(folio))
>> + device_private = MIGRATE_PFN_DEVICE;
>> migrate->src[migrate->npages] = migrate_pfn(pfn) | write
>> | MIGRATE_PFN_MIGRATE
>> - | MIGRATE_PFN_COMPOUND;
>> + | MIGRATE_PFN_COMPOUND
>> + | device_private;
>> migrate->dst[migrate->npages++] = 0;
>> migrate->cpages++;
>> ret = set_pmd_migration_entry(&pvmw, folio_page(folio, 0));
>> @@ -329,7 +333,8 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
>> }
>> mpfn = migrate_pfn(page_to_pfn(page)) |
>> - MIGRATE_PFN_MIGRATE;
>> + MIGRATE_PFN_MIGRATE |
>> + MIGRATE_PFN_DEVICE;
>
> I think this also needs to be conditional to distinguish DEVICE_COHERENT
> pages.
Agree
>
>
>> if (softleaf_is_device_private_write(entry))
>> mpfn |= MIGRATE_PFN_WRITE;
>> } else {
>> @@ -1368,7 +1373,7 @@ static unsigned long
>> migrate_device_pfn_lock(unsigned long pfn)
>> return 0;
>> }
>> - return migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
>> + return migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE | MIGRATE_PFN_DEVICE;
>
> Same here.
Maybe a page to migrate pfn helper function will be useful.
Thanks,
Jordan.
>
> Regards,
> Felix
>
>
>> }
>> /**
On 2026-01-01 at 04:03 +1100, "Kuehling, Felix" <felix.kuehling@amd.com> wrote...
> On 2025-12-30 23:31, 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
> > normal PFN and must be handled separately.
> >
> > Prepare for this by adding a MIGRATE_PFN_DEVICE flag to indicate
> > that a migrate pfn contains a PFN for a device private page.
>
> Thanks for doing this. Some comments inline regarding DEVICE_COHERENT pages.
> I suspect this will have ripple effects on the rest of the patch series, at
> least in patch 8, but I haven't looked at that in detail yet.
Thanks for catching the DEVICE_COHERENT aspects, they need to remain as real
PFNs. I think the flag should be renamed to MIGRATE_PFN_DEVICE_PRIVATE to make
this explicit.
> >
> > 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
> > ---
> > arch/powerpc/kvm/book3s_hv_uvmem.c | 2 +-
> > drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 3 ++-
> > drivers/gpu/drm/drm_pagemap.c | 2 +-
> > drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +-
> > include/linux/migrate.h | 1 +
> > lib/test_hmm.c | 4 ++--
> > mm/migrate_device.c | 11 ++++++++---
> > 7 files changed, 16 insertions(+), 9 deletions(-)
> >
> > diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
> > index e5000bef90f2..dac5d6454920 100644
> > --- a/arch/powerpc/kvm/book3s_hv_uvmem.c
> > +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
> > @@ -784,7 +784,7 @@ static int kvmppc_svm_page_in(struct vm_area_struct *vma,
> > }
> > }
> > - *mig.dst = migrate_pfn(page_to_pfn(dpage));
> > + *mig.dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_DEVICE;
> > migrate_vma_pages(&mig);
> > out_finalize:
> > migrate_vma_finalize(&mig);
> > diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> > index af53e796ea1b..0257c6e7f680 100644
> > --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> > +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> > @@ -303,7 +303,8 @@ svm_migrate_copy_to_vram(struct kfd_node *node, struct svm_range *prange,
> > dst[i] = cursor.start + (j << PAGE_SHIFT);
> > migrate->dst[i] = svm_migrate_addr_to_pfn(adev, dst[i]);
> > svm_migrate_get_vram_page(prange, migrate->dst[i]);
> > - migrate->dst[i] = migrate_pfn(migrate->dst[i]);
> > + migrate->dst[i] = migrate_pfn(migrate->dst[i]) |
> > + MIGRATE_PFN_DEVICE;
>
> On some of our GPUs we use DEVICE_COHERENT pages. These are pages that are
> coherently accessible by the CPU and peer devices in the system physical
> address space. Therefore, this needs to be conditional. Maybe add something
> like adev->kfd.migrate_pfn_flag that gets initialized conditionally in
> kgd2kfd_init_zone_device. Then add ... | adev->kfd.migrate_pfn_flag here.
I don't think you need a new flag, you could just make it conditional on
adev->kfd.pgmap.type == MEMORY_DEVICE_PRIVATE.
Note the need for this conditional is specific to the AMD driver and HMM tests -
AFAIK there are no other uses of DEVICE_COHERENT in the kernel.
- Alistair
> > mpages++;
> > }
> > spage = migrate_pfn_to_page(migrate->src[i]);
> > diff --git a/drivers/gpu/drm/drm_pagemap.c b/drivers/gpu/drm/drm_pagemap.c
> > index 37d7cfbbb3e8..0c756d73419f 100644
> > --- a/drivers/gpu/drm/drm_pagemap.c
> > +++ b/drivers/gpu/drm/drm_pagemap.c
> > @@ -404,7 +404,7 @@ int drm_pagemap_migrate_to_devmem(struct drm_pagemap_devmem *devmem_allocation,
> > struct page *page = pfn_to_page(migrate.dst[i]);
> > pages[i] = page;
> > - migrate.dst[i] = migrate_pfn(migrate.dst[i]);
> > + migrate.dst[i] = migrate_pfn(migrate.dst[i]) | MIGRATE_PFN_DEVICE;
> > drm_pagemap_get_devmem_page(page, zdd);
> > }
> > diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c b/drivers/gpu/drm/nouveau/nouveau_dmem.c
> > index 58071652679d..2bd80c6f5bcd 100644
> > --- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
> > +++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
> > @@ -766,7 +766,7 @@ static unsigned long nouveau_dmem_migrate_copy_one(struct nouveau_drm *drm,
> > ((paddr >> PAGE_SHIFT) << NVIF_VMM_PFNMAP_V0_ADDR_SHIFT);
> > if (src & MIGRATE_PFN_WRITE)
> > *pfn |= NVIF_VMM_PFNMAP_V0_W;
> > - mpfn = migrate_pfn(page_to_pfn(dpage));
> > + mpfn = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_DEVICE;
> > if (folio_order(page_folio(dpage)))
> > mpfn |= MIGRATE_PFN_COMPOUND;
> > return mpfn;
> > diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> > index 26ca00c325d9..52f65cd5c932 100644
> > --- a/include/linux/migrate.h
> > +++ b/include/linux/migrate.h
> > @@ -126,6 +126,7 @@ static inline int migrate_misplaced_folio(struct folio *folio, int node)
> > #define MIGRATE_PFN_MIGRATE (1UL << 1)
> > #define MIGRATE_PFN_WRITE (1UL << 3)
> > #define MIGRATE_PFN_COMPOUND (1UL << 4)
> > +#define MIGRATE_PFN_DEVICE (1UL << 5)
> > #define MIGRATE_PFN_SHIFT 6
> > static inline struct page *migrate_pfn_to_page(unsigned long mpfn)
> > diff --git a/lib/test_hmm.c b/lib/test_hmm.c
> > index 8af169d3873a..19681904a666 100644
> > --- a/lib/test_hmm.c
> > +++ b/lib/test_hmm.c
> > @@ -727,7 +727,7 @@ static void dmirror_migrate_alloc_and_copy(struct migrate_vma *args,
> > rpage = BACKING_PAGE(dpage);
> > rpage->zone_device_data = dmirror;
> > - *dst = migrate_pfn(page_to_pfn(dpage)) | write;
> > + *dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_DEVICE | write;
>
> This needs to be conditional on dmirror->mdevice->zone_device_type.
>
>
> > src_page = pfn_to_page(spfn + i);
> > if (spage)
> > @@ -754,7 +754,7 @@ static void dmirror_migrate_alloc_and_copy(struct migrate_vma *args,
> > pr_debug("migrating from sys to dev pfn src: 0x%lx pfn dst: 0x%lx\n",
> > page_to_pfn(spage), page_to_pfn(dpage));
> > - *dst = migrate_pfn(page_to_pfn(dpage)) | write;
> > + *dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_DEVICE | write;
>
> Same here.
>
>
> > if (is_large) {
> > int i;
> > diff --git a/mm/migrate_device.c b/mm/migrate_device.c
> > index 23379663b1e1..5d108ddf1a97 100644
> > --- a/mm/migrate_device.c
> > +++ b/mm/migrate_device.c
> > @@ -199,6 +199,7 @@ static int migrate_vma_collect_huge_pmd(pmd_t *pmdp, unsigned long start,
> > (migrate->flags & MIGRATE_VMA_SELECT_COMPOUND) &&
> > (IS_ALIGNED(start, HPAGE_PMD_SIZE) &&
> > IS_ALIGNED(end, HPAGE_PMD_SIZE))) {
> > + unsigned long device_private = 0;
> > struct page_vma_mapped_walk pvmw = {
> > .ptl = ptl,
> > @@ -208,10 +209,13 @@ static int migrate_vma_collect_huge_pmd(pmd_t *pmdp, unsigned long start,
> > };
> > unsigned long pfn = page_to_pfn(folio_page(folio, 0));
> > + if (folio_is_device_private(folio))
> > + device_private = MIGRATE_PFN_DEVICE;
> > migrate->src[migrate->npages] = migrate_pfn(pfn) | write
> > | MIGRATE_PFN_MIGRATE
> > - | MIGRATE_PFN_COMPOUND;
> > + | MIGRATE_PFN_COMPOUND
> > + | device_private;
> > migrate->dst[migrate->npages++] = 0;
> > migrate->cpages++;
> > ret = set_pmd_migration_entry(&pvmw, folio_page(folio, 0));
> > @@ -329,7 +333,8 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
> > }
> > mpfn = migrate_pfn(page_to_pfn(page)) |
> > - MIGRATE_PFN_MIGRATE;
> > + MIGRATE_PFN_MIGRATE |
> > + MIGRATE_PFN_DEVICE;
>
> I think this also needs to be conditional to distinguish DEVICE_COHERENT
> pages.
>
>
> > if (softleaf_is_device_private_write(entry))
> > mpfn |= MIGRATE_PFN_WRITE;
> > } else {
> > @@ -1368,7 +1373,7 @@ static unsigned long migrate_device_pfn_lock(unsigned long pfn)
> > return 0;
> > }
> > - return migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
> > + return migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE | MIGRATE_PFN_DEVICE;
>
> Same here.
>
> Regards,
> Felix
>
>
> > }
> > /**
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