Hi,

On 21/1/26 09:49, Zi Yan wrote:

On 20 Jan 2026, at 17:37, Jordan Niethe wrote:

quoted

Hi,

On 14/1/26 06:44, Zi Yan wrote:

quoted

On 7 Jan 2026, at 4:18, Jordan Niethe wrote:

quoted

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 modifying page_vma_mapped_walk::pfn to contain flags
as well as a PFN. Introduce a PVMW_PFN_DEVICE_PRIVATE flag to indicate
that a page_vma_mapped_walk::pfn contains a PFN for a device private
page.

Signed-off-by: Jordan Niethe <redacted>
Signed-off-by: Alistair Popple <apopple@nvidia.com>
---
v1:
    - Update for HMM huge page support
v2:
    - Move adding device_private param to check_pmd() until final patch
---
   include/linux/rmap.h | 30 +++++++++++++++++++++++++++++-
   mm/page_vma_mapped.c | 13 +++++++------
   mm/rmap.c            |  4 ++--
   mm/vmscan.c          |  2 +-
   4 files changed, 39 insertions(+), 10 deletions(-)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index daa92a58585d..57c63b6a8f65 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h

@@ -939,9 +939,37 @@ struct page_vma_mapped_walk {
   	unsigned int flags;
   };

+/* pfn is a device private offset */
+#define PVMW_PFN_DEVICE_PRIVATE	(1UL << 0)
+#define PVMW_PFN_SHIFT		1
+
+static inline unsigned long page_vma_walk_pfn(unsigned long pfn)
+{
+	return (pfn << PVMW_PFN_SHIFT);
+}
+
+static inline unsigned long folio_page_vma_walk_pfn(const struct folio *folio)
+{
+	if (folio_is_device_private(folio))
+		return page_vma_walk_pfn(folio_pfn(folio)) |
+		       PVMW_PFN_DEVICE_PRIVATE;
+
+	return page_vma_walk_pfn(folio_pfn(folio));
+}
+
+static inline struct page *page_vma_walk_pfn_to_page(unsigned long pvmw_pfn)
+{
+	return pfn_to_page(pvmw_pfn >> PVMW_PFN_SHIFT);
+}
+
+static inline struct folio *page_vma_walk_pfn_to_folio(unsigned long pvmw_pfn)
+{
+	return page_folio(page_vma_walk_pfn_to_page(pvmw_pfn));
+}
+
   #define DEFINE_FOLIO_VMA_WALK(name, _folio, _vma, _address, _flags)	\
   	struct page_vma_mapped_walk name = {				\
-		.pfn = folio_pfn(_folio),				\
+		.pfn = folio_page_vma_walk_pfn(_folio),			\
   		.nr_pages = folio_nr_pages(_folio),			\
   		.pgoff = folio_pgoff(_folio),				\
   		.vma = _vma,						\

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index b38a1d00c971..96c525785d78 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c

@@ -129,9 +129,9 @@ static bool check_pte(struct page_vma_mapped_walk *pvmw, unsigned long pte_nr)
   		pfn = softleaf_to_pfn(entry);
   	}

-	if ((pfn + pte_nr - 1) < pvmw->pfn)
+	if ((pfn + pte_nr - 1) < (pvmw->pfn >> PVMW_PFN_SHIFT))

Can you add a helper function for (pvmw->pfn >> PVMW_PFN_SHIFT)? It is impossible
to tell why pfn does not need >> PVMW_PFN_SHIFT.

Sure, something like page_vma_walk_pfn_to_offset()?

Just page_vma_walk_pfn(pvmw)? Since the code is comparing with pfn.

Sure, that works.

Thanks,
Jordan.

Best Regards,
Yan, Zi