[PATCH 1/5] mm/sparse-vmemmap: provide generic vmemmap_set_pmd() and vmemmap_check_pmd()

Muchun Song
2026-04-04T07:17:45Z

The two weak functions are currently no-ops on every architecture,
forcing each platform that needs them to duplicate the same handful
of lines. Provide a generic implementation:

- vmemmap_set_pmd() simply sets a huge PMD with PAGE_KERNEL protection.

- vmemmap_check_pmd() verifies that the PMD is present and leaf,
then calls the existing vmemmap_verify() helper.

Architectures that need special handling can continue to override the
weak symbols; everyone else gets the standard version for free.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
mm/sparse-vmemmap.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index 6eadb9d116e4..1eb990610d50 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -391,12 +391,17 @@ int __meminit vmemmap_populate_hvo(unsigned long addr, unsigned long end,
void __weak __meminit vmemmap_set_pmd(pmd_t *pmd, void *p, int node,
unsigned long addr, unsigned long next)
{
+ BUG_ON(!pmd_set_huge(pmd, virt_to_phys(p), PAGE_KERNEL));
}

int __weak __meminit vmemmap_check_pmd(pmd_t *pmd, int node,
unsigned long addr, unsigned long next)
{
- return 0;
+ if (!pmd_leaf(pmdp_get(pmd)))
+ return 0;
+ vmemmap_verify((pte_t *)pmd, node, addr, next);
+
+ return 1;
}

int __meminit vmemmap_populate_hugepages(unsigned long start, unsigned long end,
--
2.20.1