[RESEND PATCH v7 0/4] Convert x86/mm/pat to generic page table apis

[RESEND PATCH v7 0/4] Convert x86/mm/pat to generic page table apis

[Vishal Moola (Oracle)]

Replace the get_free_pages() allocation sites in set_memory.c with the
appropriate generic pagetable APIs, since the file already calls
pagetable_free() and the mismatch prevents separate allocation of ptdescs
from struct page.

Use the generic pagetable APIs consistently for both allocation and
freeing to simplify and standardize the code.

Enable Matthew’s work to allocate frozen pagetables in the short term[1],
and prepare for a clean split of ptdesc allocations from struct page in
the long term[2].

[1] https://lore.kernel.org/linux-mm/20251113140448.1814860-1-willy@infradead.org/
[2] https://lore.kernel.org/linux-mm/20251020001652.2116669-1-willy@infradead.org/

------

Based on current mm-new. Re-sending because the previous set was split
up for some reason.

v7:
  - Collect some Acks
  - Fix multi-line comment style to match the coding-style
  - Reword all messages using imperative voice (used an LLM for this)
  - CC all people found to have edited nearby lines (through git blame)

v6 link: 
https://lore.kernel.org/linux-mm/20260219020354.321088-1-vishal.moola@gmail.com/

Vishal Moola (Oracle) (4):
  x86/mm/pat: Convert pte code to use page table apis
  x86/mm/pat: Convert pmd code to use page table apis
  x86/mm/pat: Convert populate_pgd() to use page table apis
  x86/mm/pat: Convert split_large_page() to use ptdescs

 arch/x86/mm/pat/set_memory.c | 37 ++++++++++++++++++++++++------------
 1 file changed, 25 insertions(+), 12 deletions(-)

-- 
2.53.0

[RESEND PATCH v7 1/4] x86/mm/pat: Convert pte code to use page table apis

[Vishal Moola (Oracle)]

Use the ptdesc APIs for all page table allocation and free sites to allow
their separate allocation from struct page in the future. Convert the PTE
allocation and free sites to use the generic page table APIs, as they
already use ptdescs.

Pass through init_mm since these are kernel page tables; otherwise,
pte_alloc_one_kernel() becomes a no-op.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 arch/x86/mm/pat/set_memory.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 40581a720fe8..a4b1b329c23d 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1408,7 +1408,7 @@ static bool try_to_free_pte_page(pte_t *pte)
 		if (!pte_none(pte[i]))
 			return false;
 
-	free_page((unsigned long)pte);
+	pte_free_kernel(&init_mm, pte);
 	return true;
 }
 
@@ -1539,7 +1539,7 @@ static void unmap_pud_range(p4d_t *p4d, unsigned long start, unsigned long end)
 
 static int alloc_pte_page(pmd_t *pmd)
 {
-	pte_t *pte = (pte_t *)get_zeroed_page(GFP_KERNEL);
+	pte_t *pte = pte_alloc_one_kernel(&init_mm);
 	if (!pte)
 		return -1;
 
-- 
2.53.0

[RESEND PATCH v7 2/4] x86/mm/pat: Convert pmd code to use page table apis

[Vishal Moola (Oracle)]

Use the ptdesc APIs for all page table allocation and free sites to allow
their separate allocation from struct page in the future. Convert the PMD
allocation and free sites to use the generic page table APIs, as they
already use ptdescs.

Pass through init_mm since these are kernel page tables, as
pmd_alloc_one() requires it to identify kernel page tables. Because the
generic implementation does not use the second argument, pass a
placeholder to avoid reimplementing it or risking breakage on other
architectures.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 arch/x86/mm/pat/set_memory.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index a4b1b329c23d..72a260007996 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1420,7 +1420,7 @@ static bool try_to_free_pmd_page(pmd_t *pmd)
 		if (!pmd_none(pmd[i]))
 			return false;
 
-	free_page((unsigned long)pmd);
+	pmd_free(&init_mm, pmd);
 	return true;
 }
 
@@ -1549,7 +1549,11 @@ static int alloc_pte_page(pmd_t *pmd)
 
 static int alloc_pmd_page(pud_t *pud)
 {
-	pmd_t *pmd = (pmd_t *)get_zeroed_page(GFP_KERNEL);
+	/*
+	 * Pass 0 as a placeholder for the second argument, since the
+	 * generic implementation of pmd_alloc_one() does not use it.
+	 */
+	pmd_t *pmd = pmd_alloc_one(&init_mm, 0);
 	if (!pmd)
 		return -1;
 
-- 
2.53.0

[RESEND PATCH v7 3/4] x86/mm/pat: Convert populate_pgd() to use page table apis

[Vishal Moola (Oracle)]

Use the ptdesc APIs for all page table allocation and free sites to allow
their separate allocation from struct page in the future. Convert the
remaining get_zeroed_page() calls to the generic page table APIs, as they
already use ptdescs.

Pass through init_mm since these are kernel page tables, as
both functions require it to identify kernel page tables. Because the
generic implementations do not use the second argument, pass a
placeholder to avoid reimplementing them or risking breakage on other
architectures.

It is not obvious whether these pages are freed. Regardless, convert the
remaining free paths as needed, noting that the only other possible free
paths have already been converted and that a frozen page table test
kernel has not reported any issues.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 arch/x86/mm/pat/set_memory.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 72a260007996..17c1c28e3491 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1747,7 +1747,11 @@ static int populate_pgd(struct cpa_data *cpa, unsigned long addr)
 	pgd_entry = cpa->pgd + pgd_index(addr);
 
 	if (pgd_none(*pgd_entry)) {
-		p4d = (p4d_t *)get_zeroed_page(GFP_KERNEL);
+		/*
+		 * Pass 0 as a placeholder for the second argument, since the
+		 * generic implementation of p4d_alloc_one() does not use it.
+		 */
+		p4d = p4d_alloc_one(&init_mm, 0);
 		if (!p4d)
 			return -1;
 
@@ -1759,7 +1763,11 @@ static int populate_pgd(struct cpa_data *cpa, unsigned long addr)
 	 */
 	p4d = p4d_offset(pgd_entry, addr);
 	if (p4d_none(*p4d)) {
-		pud = (pud_t *)get_zeroed_page(GFP_KERNEL);
+		/*
+		 * Pass 0 as a placeholder for the second argument, since the
+		 * generic implementation of pud_alloc_one() does not use it.
+		 */
+		pud = pud_alloc_one(&init_mm, 0);
 		if (!pud)
 			return -1;
 
-- 
2.53.0

[RESEND PATCH v7 4/4] x86/mm/pat: Convert split_large_page() to use ptdescs

[Vishal Moola (Oracle)]

Use the ptdesc APIs for all page table allocation and free sites to
allow their separate allocation from struct page in the future.

Update split_large_page() to allocate a ptdesc instead of allocating a
page for use as a page table.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 arch/x86/mm/pat/set_memory.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 17c1c28e3491..cba907c39718 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1119,9 +1119,10 @@ static void split_set_pte(struct cpa_data *cpa, pte_t *pte, unsigned long pfn,
 
 static int
 __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address,
-		   struct page *base)
+		   struct ptdesc *ptdesc)
 {
 	unsigned long lpaddr, lpinc, ref_pfn, pfn, pfninc = 1;
+	struct page *base = ptdesc_page(ptdesc);
 	pte_t *pbase = (pte_t *)page_address(base);
 	unsigned int i, level;
 	pgprot_t ref_prot;
@@ -1226,18 +1227,18 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address,
 static int split_large_page(struct cpa_data *cpa, pte_t *kpte,
 			    unsigned long address)
 {
-	struct page *base;
+	struct ptdesc *ptdesc;
 
 	if (!debug_pagealloc_enabled())
 		spin_unlock(&cpa_lock);
-	base = alloc_pages(GFP_KERNEL, 0);
+	ptdesc = pagetable_alloc(GFP_KERNEL, 0);
 	if (!debug_pagealloc_enabled())
 		spin_lock(&cpa_lock);
-	if (!base)
+	if (!ptdesc)
 		return -ENOMEM;
 
-	if (__split_large_page(cpa, kpte, address, base))
-		__free_page(base);
+	if (__split_large_page(cpa, kpte, address, ptdesc))
+		pagetable_free(ptdesc);
 
 	return 0;
 }
-- 
2.53.0