From: Anshuman Khandual <anshuman.khandual@arm.com>
Date: Fri, 27 Feb 2026 06:27:44 +0000 (+0000)
Subject: perf/events: Replace READ_ONCE() with standard pgtable accessors
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=5a84b600050c5f16b8bba25dd0e7aea845880407;p=thirdparty%2Fkernel%2Flinux.git

perf/events: Replace READ_ONCE() with standard pgtable accessors

Replace raw READ_ONCE() dereferences of pgtable entries with corresponding
standard page table accessors pxdp_get() in perf_get_pgtable_size(). These
accessors default to READ_ONCE() on platforms that don't override them. So
there is no functional change on such platforms.

However arm64 platform is being extended to support 128 bit page tables via
a new architecture feature i.e FEAT_D128 in which case READ_ONCE() will not
provide required single copy atomic access for 128 bit page table entries.
Although pxdp_get() accessors can later be overridden on arm64 platform to
extend required single copy atomicity support on 128 bit entries.

Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260227062744.2215491-1-anshuman.khandual@arm.com
---

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 5eeae8636996c..95d7a3e57268b 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8421,7 +8421,7 @@ static u64 perf_get_pgtable_size(struct mm_struct *mm, unsigned long addr)
 	pte_t *ptep, pte;
 
 	pgdp = pgd_offset(mm, addr);
-	pgd = READ_ONCE(*pgdp);
+	pgd = pgdp_get(pgdp);
 	if (pgd_none(pgd))
 		return 0;
 
@@ -8429,7 +8429,7 @@ static u64 perf_get_pgtable_size(struct mm_struct *mm, unsigned long addr)
 		return pgd_leaf_size(pgd);
 
 	p4dp = p4d_offset_lockless(pgdp, pgd, addr);
-	p4d = READ_ONCE(*p4dp);
+	p4d = p4dp_get(p4dp);
 	if (!p4d_present(p4d))
 		return 0;
 
@@ -8437,7 +8437,7 @@ static u64 perf_get_pgtable_size(struct mm_struct *mm, unsigned long addr)
 		return p4d_leaf_size(p4d);
 
 	pudp = pud_offset_lockless(p4dp, p4d, addr);
-	pud = READ_ONCE(*pudp);
+	pud = pudp_get(pudp);
 	if (!pud_present(pud))
 		return 0;