linux-kernel - [PATCH] fixup: mm/rmap: extend rmap and migration support device-private entries

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Message-ID: <20251115002835.3515194-1-balbirs@nvidia.com>
Date: Sat, 15 Nov 2025 11:28:35 +1100
From: Balbir Singh <balbirs@...dia.com>
To: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	dri-devel@...ts.freedesktop.org
Cc: Balbir Singh <balbirs@...dia.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...hat.com>,
	Zi Yan <ziy@...dia.com>,
	Joshua Hahn <joshua.hahnjy@...il.com>,
	Rakie Kim <rakie.kim@...com>,
	Byungchul Park <byungchul@...com>,
	Gregory Price <gourry@...rry.net>,
	Ying Huang <ying.huang@...ux.alibaba.com>,
	Alistair Popple <apopple@...dia.com>,
	Oscar Salvador <osalvador@...e.de>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Nico Pache <npache@...hat.com>,
	Ryan Roberts <ryan.roberts@....com>,
	Dev Jain <dev.jain@....com>,
	Barry Song <baohua@...nel.org>,
	Lyude Paul <lyude@...hat.com>,
	Danilo Krummrich <dakr@...nel.org>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	Ralph Campbell <rcampbell@...dia.com>,
	Mika Penttilä <mpenttil@...hat.com>,
	Matthew Brost <matthew.brost@...el.com>,
	Francois Dugast <francois.dugast@...el.com>
Subject: [PATCH] fixup: mm/rmap: extend rmap and migration support device-private entries

Follow the pattern used in remove_migration_pte() in
remove_migration_pmd(). Process the migration entries and if the entry
type is device private, override the pmde with a device private entry
and set the soft dirty and uffd_wp bits with the pmd_swp_mksoft_dirty
and pmd_swp_mkuffd_wp

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: David Hildenbrand <david@...hat.com>
Cc: Zi Yan <ziy@...dia.com>
Cc: Joshua Hahn <joshua.hahnjy@...il.com>
Cc: Rakie Kim <rakie.kim@...com>
Cc: Byungchul Park <byungchul@...com>
Cc: Gregory Price <gourry@...rry.net>
Cc: Ying Huang <ying.huang@...ux.alibaba.com>
Cc: Alistair Popple <apopple@...dia.com>
Cc: Oscar Salvador <osalvador@...e.de>
Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc: Nico Pache <npache@...hat.com>
Cc: Ryan Roberts <ryan.roberts@....com>
Cc: Dev Jain <dev.jain@....com>
Cc: Barry Song <baohua@...nel.org>
Cc: Lyude Paul <lyude@...hat.com>
Cc: Danilo Krummrich <dakr@...nel.org>
Cc: David Airlie <airlied@...il.com>
Cc: Simona Vetter <simona@...ll.ch>
Cc: Ralph Campbell <rcampbell@...dia.com>
Cc: Mika Penttilä <mpenttil@...hat.com>
Cc: Matthew Brost <matthew.brost@...el.com>
Cc: Francois Dugast <francois.dugast@...el.com>

Signed-off-by: Balbir Singh <balbirs@...dia.com>
---
This fixup should be squashed into the patch "mm/rmap: extend rmap and
migration support" of mm/mm-unstable

 mm/huge_memory.c | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 9dda8c48daca..50ba458efcab 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -4698,16 +4698,6 @@ void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
 	folio_get(folio);
 	pmde = folio_mk_pmd(folio, READ_ONCE(vma->vm_page_prot));

-	if (folio_is_device_private(folio)) {
-		if (pmd_write(pmde))
-			entry = make_writable_device_private_entry(
-							page_to_pfn(new));
-		else
-			entry = make_readable_device_private_entry(
-							page_to_pfn(new));
-		pmde = swp_entry_to_pmd(entry);
-	}
-
 	if (pmd_swp_soft_dirty(*pvmw->pmd))
 		pmde = pmd_mksoft_dirty(pmde);
 	if (is_writable_migration_entry(entry))
@@ -4720,6 +4710,23 @@ void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
 	if (folio_test_dirty(folio) && is_migration_entry_dirty(entry))
 		pmde = pmd_mkdirty(pmde);

+	if (folio_is_device_private(folio)) {
+		swp_entry_t entry;
+
+		if (pmd_write(pmde))
+			entry = make_writable_device_private_entry(
+							page_to_pfn(new));
+		else
+			entry = make_readable_device_private_entry(
+							page_to_pfn(new));
+		pmde = swp_entry_to_pmd(entry);
+
+		if (pmd_swp_soft_dirty(*pvmw->pmd))
+			pmde = pmd_swp_mksoft_dirty(pmde);
+		if (pmd_swp_uffd_wp(*pvmw->pmd))
+			pmde = pmd_swp_mkuffd_wp(pmde);
+	}
+
 	if (folio_test_anon(folio)) {
 		rmap_t rmap_flags = RMAP_NONE;

-- 
2.51.1