[tip: x86/mm] x86/mm/pae: Don't (ab)use atomic64

[tip-bot2 for Peter Zijlstra]

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

Commit-ID:     7a9b8bdb6af3e19fb8e3dc7a3caf6a9ea1bed8cd
Gitweb:        https://git.kernel.org/tip/7a9b8bdb6af3e19fb8e3dc7a3caf6a9ea1bed8cd
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Thu, 26 Nov 2020 17:38:42 +01:00
Committer:     Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
CommitterDate: Thu, 15 Dec 2022 10:37:27 -08:00

x86/mm/pae: Don't (ab)use atomic64

PAE implies CX8, write readable code.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20221022114424.971450128%40infradead.org
---
 arch/x86/include/asm/pgtable-3level.h |  9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/pgtable-3level.h b/arch/x86/include/asm/pgtable-3level.h
index 94f50b0..0a1b81d 100644
--- a/arch/x86/include/asm/pgtable-3level.h
+++ b/arch/x86/include/asm/pgtable-3level.h
@@ -2,8 +2,6 @@
 #ifndef _ASM_X86_PGTABLE_3LEVEL_H
 #define _ASM_X86_PGTABLE_3LEVEL_H
 
-#include <asm/atomic64_32.h>
-
 /*
  * Intel Physical Address Extension (PAE) Mode - three-level page
  * tables on PPro+ CPUs.
@@ -95,11 +93,12 @@ static inline void pud_clear(pud_t *pudp)
 #ifdef CONFIG_SMP
 static inline pte_t native_ptep_get_and_clear(pte_t *ptep)
 {
-	pte_t res;
+	pte_t old = *ptep;
 
-	res.pte = (pteval_t)arch_atomic64_xchg((atomic64_t *)ptep, 0);
+	do {
+	} while (!try_cmpxchg64(&ptep->pte, &old.pte, 0ULL));
 
-	return res;
+	return old;
 }
 #else
 #define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp)