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Message-ID: <20250903011900.3657435-4-balbirs@nvidia.com>
Date: Wed, 3 Sep 2025 11:18:48 +1000
From: Balbir Singh <balbirs@...dia.com>
To: linux-kernel@...r.kernel.org,
linux-mm@...ck.org
Cc: damon@...ts.linux.dev,
dri-devel@...ts.freedesktop.org,
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: [v4 03/15] mm/rmap: extend rmap and migration support device-private entries
Add device-private THP support to reverse mapping infrastructure,
enabling proper handling during migration and walk operations.
The key changes are:
- add_migration_pmd()/remove_migration_pmd(): Handle device-private
entries during folio migration and splitting
- page_vma_mapped_walk(): Recognize device-private THP entries during
VMA traversal operations
This change supports folio splitting and migration operations on
device-private entries.
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>
---
mm/damon/ops-common.c | 20 +++++++++++++++++---
mm/huge_memory.c | 16 +++++++++++++++-
mm/page_idle.c | 5 +++--
mm/page_vma_mapped.c | 12 ++++++++++--
mm/rmap.c | 19 ++++++++++++++++---
5 files changed, 61 insertions(+), 11 deletions(-)
diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c
index 99321ff5cb92..14ec6591074f 100644
--- a/mm/damon/ops-common.c
+++ b/mm/damon/ops-common.c
@@ -75,12 +75,24 @@ void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned long addr
void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma, unsigned long addr)
{
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- struct folio *folio = damon_get_folio(pmd_pfn(pmdp_get(pmd)));
+ pmd_t pmdval = pmdp_get(pmd);
+ struct folio *folio;
+ bool young = false;
+ unsigned long pfn;
+
+ if (likely(pmd_present(pmdval)))
+ pfn = pmd_pfn(pmdval);
+ else
+ pfn = swp_offset_pfn(pmd_to_swp_entry(pmdval));
+ folio = damon_get_folio(pfn);
if (!folio)
return;
- if (pmdp_clear_young_notify(vma, addr, pmd))
+ if (likely(pmd_present(pmdval)))
+ young |= pmdp_clear_young_notify(vma, addr, pmd);
+ young |= mmu_notifier_clear_young(vma->vm_mm, addr, addr + PAGE_SIZE);
+ if (young)
folio_set_young(folio);
folio_set_idle(folio);
@@ -203,7 +215,9 @@ static bool damon_folio_young_one(struct folio *folio,
mmu_notifier_test_young(vma->vm_mm, addr);
} else {
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- *accessed = pmd_young(pmdp_get(pvmw.pmd)) ||
+ pmd_t pmd = pmdp_get(pvmw.pmd);
+
+ *accessed = (pmd_present(pmd) && pmd_young(pmd)) ||
!folio_test_idle(folio) ||
mmu_notifier_test_young(vma->vm_mm, addr);
#else
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 4acdedf84fe6..0c811d34f418 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -4649,7 +4649,10 @@ int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
return 0;
flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
- pmdval = pmdp_invalidate(vma, address, pvmw->pmd);
+ if (unlikely(!pmd_present(*pvmw->pmd)))
+ pmdval = pmdp_huge_get_and_clear(vma->vm_mm, address, pvmw->pmd);
+ else
+ pmdval = pmdp_invalidate(vma, address, pvmw->pmd);
/* See folio_try_share_anon_rmap_pmd(): invalidate PMD first. */
anon_exclusive = folio_test_anon(folio) && PageAnonExclusive(page);
@@ -4699,6 +4702,17 @@ void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
entry = pmd_to_swp_entry(*pvmw->pmd);
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))
diff --git a/mm/page_idle.c b/mm/page_idle.c
index a82b340dc204..9030c31800ce 100644
--- a/mm/page_idle.c
+++ b/mm/page_idle.c
@@ -71,8 +71,9 @@ static bool page_idle_clear_pte_refs_one(struct folio *folio,
referenced |= ptep_test_and_clear_young(vma, addr, pvmw.pte);
referenced |= mmu_notifier_clear_young(vma->vm_mm, addr, addr + PAGE_SIZE);
} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
- if (pmdp_clear_young_notify(vma, addr, pvmw.pmd))
- referenced = true;
+ if (likely(pmd_present(pmdp_get(pvmw.pmd))))
+ referenced |= pmdp_clear_young_notify(vma, addr, pvmw.pmd);
+ referenced |= mmu_notifier_clear_young(vma->vm_mm, addr, addr + PAGE_SIZE);
} else {
/* unexpected pmd-mapped page? */
WARN_ON_ONCE(1);
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index e981a1a292d2..7ab46a2b4e15 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -250,12 +250,11 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
pvmw->ptl = pmd_lock(mm, pvmw->pmd);
pmde = *pvmw->pmd;
if (!pmd_present(pmde)) {
- swp_entry_t entry;
+ swp_entry_t entry = pmd_to_swp_entry(pmde);
if (!thp_migration_supported() ||
!(pvmw->flags & PVMW_MIGRATION))
return not_found(pvmw);
- entry = pmd_to_swp_entry(pmde);
if (!is_migration_entry(entry) ||
!check_pmd(swp_offset_pfn(entry), pvmw))
return not_found(pvmw);
@@ -277,6 +276,15 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
* cannot return prematurely, while zap_huge_pmd() has
* cleared *pmd but not decremented compound_mapcount().
*/
+ swp_entry_t entry;
+
+ entry = pmd_to_swp_entry(pmde);
+
+ if (is_device_private_entry(entry)) {
+ pvmw->ptl = pmd_lock(mm, pvmw->pmd);
+ return true;
+ }
+
if ((pvmw->flags & PVMW_SYNC) &&
thp_vma_suitable_order(vma, pvmw->address,
PMD_ORDER) &&
diff --git a/mm/rmap.c b/mm/rmap.c
index b5837075b6e0..196a542f983c 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1064,8 +1064,10 @@ static int page_vma_mkclean_one(struct page_vma_mapped_walk *pvmw)
} else {
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
pmd_t *pmd = pvmw->pmd;
- pmd_t entry;
+ pmd_t entry = pmdp_get(pmd);
+ if (!pmd_present(entry))
+ continue;
if (!pmd_dirty(*pmd) && !pmd_write(*pmd))
continue;
@@ -2330,6 +2332,11 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
while (page_vma_mapped_walk(&pvmw)) {
/* PMD-mapped THP migration entry */
if (!pvmw.pte) {
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+ unsigned long pfn;
+ pmd_t pmdval;
+#endif
+
if (flags & TTU_SPLIT_HUGE_PMD) {
split_huge_pmd_locked(vma, pvmw.address,
pvmw.pmd, true);
@@ -2338,8 +2345,14 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
break;
}
#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
- subpage = folio_page(folio,
- pmd_pfn(*pvmw.pmd) - folio_pfn(folio));
+ pmdval = pmdp_get(pvmw.pmd);
+ if (likely(pmd_present(pmdval)))
+ pfn = pmd_pfn(pmdval);
+ else
+ pfn = swp_offset_pfn(pmd_to_swp_entry(pmdval));
+
+ subpage = folio_page(folio, pfn - folio_pfn(folio));
+
VM_BUG_ON_FOLIO(folio_test_hugetlb(folio) ||
!folio_test_pmd_mappable(folio), folio);
--
2.50.1
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