[PATCH v3] x86: Align TLB invalidation info

[PATCH v3] x86: Align TLB invalidation info

[Nadav Amit]

The TLB invalidation info is allocated on the stack, which might cause
it to be unaligned. Since this information may be transferred to
different cores for TLB shootdown, this may cause an additional cache
line to become shared. While the overhead is likely to be small, the
fix is simple.

We do not use __cacheline_aligned() since it also defines the section,
which is inappropriate for stack variables.

Signed-off-by: Nadav Amit <namit@vmware.com>
Acked-by: Andy Lutomirski <luto@kernel.org>

Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>

--
v2 -> v3: rewording the commit message (Andy)
v1 -> v2: use __aligned instead of all the mess (Andy)
---
 arch/x86/mm/tlb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 5bfe61a5e8e3..9690112e3a82 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -576,7 +576,7 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
 {
 	int cpu;
 
-	struct flush_tlb_info info = {
+	struct flush_tlb_info info __aligned(SMP_CACHE_BYTES) = {
 		.mm = mm,
 	};
 
-- 
2.14.1

[tip:x86/mm] x86/mm: Align TLB invalidation info

[tip-bot for Nadav Amit]

Commit-ID:  515ab7c41306aad1f80a980e1936ef635c61570c
Gitweb:     https://git.kernel.org/tip/515ab7c41306aad1f80a980e1936ef635c61570c
Author:     Nadav Amit <namit@vmware.com>
AuthorDate: Wed, 31 Jan 2018 13:19:12 -0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 13 Feb 2018 15:05:49 +0100

x86/mm: Align TLB invalidation info

The TLB invalidation info is allocated on the stack, which might cause
it to be unaligned. Since this information may be transferred to
different cores for TLB shootdown, this may cause an additional cache
line to become shared. While the overhead is likely to be small, the
fix is simple.

We do not use __cacheline_aligned() since it also defines the section,
which is inappropriate for stack variables.

Signed-off-by: Nadav Amit <namit@vmware.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180131211912.52064-1-namit@vmware.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/mm/tlb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 8dcc060..6550d37 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -613,7 +613,7 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
 {
 	int cpu;
 
-	struct flush_tlb_info info = {
+	struct flush_tlb_info info __aligned(SMP_CACHE_BYTES) = {
 		.mm = mm,
 	};