linux-kernel - [tip: x86/mm] x86/mm: Preallocate all PAE page tables

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <174491300499.31282.12749824705521273948.tip-bot2@tip-bot2>
Date: Thu, 17 Apr 2025 18:03:24 -0000
From: "tip-bot2 for Dave Hansen" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: x86/mm] x86/mm: Preallocate all PAE page tables

The following commit has been merged into the x86/mm branch of tip:

Commit-ID:     454e65b4fb38ddeea62472649ef16b5e8d285015
Gitweb:        https://git.kernel.org/tip/454e65b4fb38ddeea62472649ef16b5e8d285015
Author:        Dave Hansen <dave.hansen@...ux.intel.com>
AuthorDate:    Mon, 14 Apr 2025 10:32:41 -07:00
Committer:     Dave Hansen <dave.hansen@...ux.intel.com>
CommitterDate: Thu, 17 Apr 2025 10:39:25 -07:00

x86/mm: Preallocate all PAE page tables

Finally, move away from having PAE kernels share any PMDs across
processes.

This was already the default on PTI kernels which are  the common
case.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Link: https://lore.kernel.org/all/20250414173241.1288CAB4%40davehans-spike.ostc.intel.com
---
 arch/x86/mm/pgtable.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index ca07db5..f4fa8fa 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -80,16 +80,11 @@ struct mm_struct *pgd_page_get_mm(struct page *page)
 
 static void pgd_ctor(struct mm_struct *mm, pgd_t *pgd)
 {
-	/* If the pgd points to a shared pagetable level (either the
-	   ptes in non-PAE, or shared PMD in PAE), then just copy the
-	   references from swapper_pg_dir. */
-	if (CONFIG_PGTABLE_LEVELS == 2 ||
-	    (CONFIG_PGTABLE_LEVELS == 3 && SHARED_KERNEL_PMD) ||
-	    CONFIG_PGTABLE_LEVELS >= 4) {
+	/* PAE preallocates all its PMDs.  No cloning needed. */
+	if (!IS_ENABLED(CONFIG_X86_PAE))
 		clone_pgd_range(pgd + KERNEL_PGD_BOUNDARY,
 				swapper_pg_dir + KERNEL_PGD_BOUNDARY,
 				KERNEL_PGD_PTRS);
-	}
 
 	/* List used to sync kernel mapping updates */
 	pgd_set_mm(pgd, mm);
@@ -122,8 +117,7 @@ static void pgd_dtor(pgd_t *pgd)
  * all 4 top-level entries are used almost immediately in a
  * new process's life, we just pre-populate them here.
  */
-#define PREALLOCATED_PMDS	(static_cpu_has(X86_FEATURE_PTI) ? \
-					PTRS_PER_PGD : KERNEL_PGD_BOUNDARY)
+#define PREALLOCATED_PMDS	PTRS_PER_PGD
 #define MAX_PREALLOCATED_PMDS	PTRS_PER_PGD
 
 /*