From: Peter Zijlstra <peterz@infradead.org>
Date: Tue, 5 Dec 2017 13:34:46 +0100
Subject: x86/mm: Remove superfluous barriers
Git-commit: b5fc6d943808b570bdfbec80f40c6b3855f1c48b
Patch-mainline: v4.15-rc5
References: bsc#1068032 CVE-2017-5754
atomic64_inc_return() already implies smp_mb() before and after.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: linux-mm@kvack.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov <bp@suse.de>
---
arch/x86/include/asm/tlbflush.h | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -59,19 +59,13 @@ static inline void invpcid_flush_all_non
static inline u64 inc_mm_tlb_gen(struct mm_struct *mm)
{
- u64 new_tlb_gen;
-
/*
* Bump the generation count. This also serves as a full barrier
* that synchronizes with switch_mm(): callers are required to order
* their read of mm_cpumask after their writes to the paging
* structures.
*/
- smp_mb__before_atomic();
- new_tlb_gen = atomic64_inc_return(&mm->context.tlb_gen);
- smp_mb__after_atomic();
-
- return new_tlb_gen;
+ return atomic64_inc_return(&mm->context.tlb_gen);
}
#ifdef CONFIG_PARAVIRT