On 2/5/25 20:39, Ryan Roberts wrote:

Refactor __set_ptes(), set_pmd_at() and set_pud_at() so that they are
all a thin wrapper around a generic ___set_ptes(), which takes pgsize

s/generic/common - as generic might be misleading for being generic MM.

parameter. This cleans up the code to remove the confusing
__set_pte_at() (which was only ever used for pmd/pud) and will allow us
to perform future barrier optimizations in a single place. Additionally,
it will permit the huge_pte API to efficiently batch-set pgtable entries
and take advantage of the future barrier optimizations.

Makes sense.

___set_ptes() calls the correct page_table_check_*_set() function based
on the pgsize. This means that huge_ptes be able to get proper coverage
regardless of their size, once it's plumbed into huge_pte. Currently the
huge_pte API always uses the pte API which assumes an entry only covers
a single page.

Right

While we are at it, refactor __ptep_get_and_clear() and
pmdp_huge_get_and_clear() to use a common ___ptep_get_and_clear() which
also takes a pgsize parameter. This will provide the huge_pte API the
means to clear ptes corresponding with the way they were set.

__ptep_get_and_clear() refactoring does not seem to be related to the
previous __set_ptes(). Should they be separated out into two different
patches instead - for better clarity and review ? Both these clean ups
have enough change and can stand own their own.

So address got dropped and page size got added as an argument.
s/___set_ptes/___set_pxds ? to be more generic for all levels.

 {
-	__sync_cache_and_tags(pte, nr);
-	__check_safe_pte_update(mm, ptep, pte);
-	__set_pte(ptep, pte);
+	unsigned long stride = pgsize >> PAGE_SHIFT;
+
+	switch (pgsize) {
+	case PAGE_SIZE:
+		page_table_check_ptes_set(mm, ptep, pte, nr);
+		break;
+	case PMD_SIZE:
+		page_table_check_pmds_set(mm, (pmd_t *)ptep, pte_pmd(pte), nr);
+		break;
+	case PUD_SIZE:
+		page_table_check_puds_set(mm, (pud_t *)ptep, pte_pud(pte), nr);
+		break;

This is where the new page table check APIs get used for batch testing.

+	default:
+		VM_WARN_ON(1);
+	}
+
+	__sync_cache_and_tags(pte, nr * stride);
+
+	for (;;) {
+		__check_safe_pte_update(mm, ptep, pte);
+		__set_pte(ptep, pte);
+		if (--nr == 0)
+			break;
+		ptep++;
+		pte = pte_advance_pfn(pte, stride);
+	}
 }

LGTM

 
-static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
-			      pmd_t *pmdp, pmd_t pmd)
+static inline void __set_ptes(struct mm_struct *mm,
+			      unsigned long __always_unused addr,
+			      pte_t *ptep, pte_t pte, unsigned int nr)
 {
-	page_table_check_pmd_set(mm, pmdp, pmd);
-	return __set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd),
-						PMD_SIZE >> PAGE_SHIFT);
+	___set_ptes(mm, ptep, pte, nr, PAGE_SIZE);
 }
 
-static inline void set_pud_at(struct mm_struct *mm, unsigned long addr,
-			      pud_t *pudp, pud_t pud)
+static inline void __set_pmds(struct mm_struct *mm,
+			      unsigned long __always_unused addr,
+			      pmd_t *pmdp, pmd_t pmd, unsigned int nr)
+{
+	___set_ptes(mm, (pte_t *)pmdp, pmd_pte(pmd), nr, PMD_SIZE);
+}
+#define set_pmd_at(mm, addr, pmdp, pmd) __set_pmds(mm, addr, pmdp, pmd, 1)
+
+static inline void __set_puds(struct mm_struct *mm,
+			      unsigned long __always_unused addr,
+			      pud_t *pudp, pud_t pud, unsigned int nr)
 {
-	page_table_check_pud_set(mm, pudp, pud);
-	return __set_pte_at(mm, addr, (pte_t *)pudp, pud_pte(pud),
-						PUD_SIZE >> PAGE_SHIFT);
+	___set_ptes(mm, (pte_t *)pudp, pud_pte(pud), nr, PUD_SIZE);
 }
+#define set_pud_at(mm, addr, pudp, pud) __set_puds(mm, addr, pudp, pud, 1)

LGTM

So address got dropped and page size got added as an argument.

Although currently there is no pudp_huge_get_and_clear() helper on arm64
reworked ___ptep_get_and_clear() will be able to support that as well if
and when required as it now supports PUD_SIZE page size.