linux-kernel - [PATCH v4 3/4] x86/mm/pat: Convert pmd code to use ptdescs

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Message-ID: <20260205013527.322157-4-vishal.moola@gmail.com>
Date: Wed,  4 Feb 2026 17:35:26 -0800
From: "Vishal Moola (Oracle)" <vishal.moola@...il.com>
To: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	x86@...nel.org,
	"Mike Rapoport (Microsoft)" <rppt@...nel.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>
Cc: akpm@...ux-foundation.org,
	"Matthew Wilcox (Oracle)" <willy@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"Vishal Moola (Oracle)" <vishal.moola@...il.com>
Subject: [PATCH v4 3/4] x86/mm/pat: Convert pmd code to use ptdescs

We need all allocation and free sites to use the ptdesc APIs in order to
allocate them separately from regular pages. Convert these pmd
allocation/free sites to use ptdescs.

populate_pgd() also allocates pagetables that may later be freed by
try_to_free_pmd_page(), so allocate ptdescs there as well.

Also, rename *_pmd_page() functions to *_pmd(). Rename them now to avoid
any confusion later. Eventually these allocations will be backed by a
ptdesc not a page, but that's not important to callers either.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@...il.com>
---
 arch/x86/mm/pat/set_memory.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index c6c68fbbb046..dfe05cdf460c 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1412,7 +1412,7 @@ static bool try_to_free_pte(pte_t *pte)
 	return true;
 }
 
-static bool try_to_free_pmd_page(pmd_t *pmd)
+static bool try_to_free_pmd(pmd_t *pmd)
 {
 	int i;
 
@@ -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);
+	pgtable_free_addr(pmd);
 	return true;
 }
 
@@ -1446,7 +1446,7 @@ static void __unmap_pmd_range(pud_t *pud, pmd_t *pmd,
 			      unsigned long start, unsigned long end)
 {
 	if (unmap_pte_range(pmd, start, end))
-		if (try_to_free_pmd_page(pud_pgtable(*pud)))
+		if (try_to_free_pmd(pud_pgtable(*pud)))
 			pud_clear(pud);
 }
 
@@ -1490,7 +1490,7 @@ static void unmap_pmd_range(pud_t *pud, unsigned long start, unsigned long end)
 	 * Try again to free the PMD page if haven't succeeded above.
 	 */
 	if (!pud_none(*pud))
-		if (try_to_free_pmd_page(pud_pgtable(*pud)))
+		if (try_to_free_pmd(pud_pgtable(*pud)))
 			pud_clear(pud);
 }
 
@@ -1547,9 +1547,9 @@ static int alloc_pte(pmd_t *pmd)
 	return 0;
 }
 
-static int alloc_pmd_page(pud_t *pud)
+static int alloc_pmd(pud_t *pud)
 {
-	pmd_t *pmd = (pmd_t *)get_zeroed_page(GFP_KERNEL);
+	pmd_t *pmd = (pmd_t *) pgtable_alloc_addr(GFP_KERNEL, 0);
 	if (!pmd)
 		return -1;
 
@@ -1622,7 +1622,7 @@ static long populate_pmd(struct cpa_data *cpa,
 		 * We cannot use a 1G page so allocate a PMD page if needed.
 		 */
 		if (pud_none(*pud))
-			if (alloc_pmd_page(pud))
+			if (alloc_pmd(pud))
 				return -1;
 
 		pmd = pmd_offset(pud, start);
@@ -1678,7 +1678,7 @@ static int populate_pud(struct cpa_data *cpa, unsigned long start, p4d_t *p4d,
 		 * Need a PMD page?
 		 */
 		if (pud_none(*pud))
-			if (alloc_pmd_page(pud))
+			if (alloc_pmd(pud))
 				return -1;
 
 		cur_pages = populate_pmd(cpa, start, pre_end, cur_pages,
@@ -1715,7 +1715,7 @@ static int populate_pud(struct cpa_data *cpa, unsigned long start, p4d_t *p4d,
 
 		pud = pud_offset(p4d, start);
 		if (pud_none(*pud))
-			if (alloc_pmd_page(pud))
+			if (alloc_pmd(pud))
 				return -1;
 
 		tmp = populate_pmd(cpa, start, end, cpa->numpages - cur_pages,
@@ -1743,7 +1743,7 @@ 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);
+		p4d = (p4d_t *)pgtable_alloc_addr(GFP_KERNEL, 0);
 		if (!p4d)
 			return -1;
 
@@ -1755,7 +1755,7 @@ 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);
+		pud = (pud_t *)pgtable_alloc_addr(GFP_KERNEL, 0);
 		if (!pud)
 			return -1;
 
-- 
2.52.0