linux-kernel - [PATCH 4.1 04/65] x86/mm: If INVPCID is available, use it to flush global mappings

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Date:   Mon,  5 Mar 2018 19:24:37 -0500
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     steven.sistare@...cle.com, daniel.m.jordan@...cle.com,
        linux-kernel@...r.kernel.org, Alexander.Levin@...rosoft.com,
        dan.j.williams@...el.com, sathyanarayanan.kuppuswamy@...el.com,
        pankaj.laxminarayan.bharadiya@...el.com, akuster@...sta.com,
        cminyard@...sta.com, pasha.tatashin@...cle.com,
        gregkh@...uxfoundation.org, stable@...r.kernel.org
Subject: [PATCH 4.1 04/65] x86/mm: If INVPCID is available, use it to flush global mappings

From: Andy Lutomirski <luto@...nel.org>

commit d8bced79af1db6734f66b42064cc773cada2ce99 upstream.

On my Skylake laptop, INVPCID function 2 (flush absolutely
everything) takes about 376ns, whereas saving flags, twiddling
CR4.PGE to flush global mappings, and restoring flags takes about
539ns.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
Reviewed-by: Borislav Petkov <bp@...e.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@...e.com>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Toshi Kani <toshi.kani@...com>
Cc: linux-mm@...ck.org
Link: http://lkml.kernel.org/r/ed0ef62581c0ea9c99b9bf6df726015e96d44743.1454096309.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
(cherry picked from commit 85d3700c744a11ee2989252acf50ccbbd814167a)
Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>
---
 arch/x86/include/asm/tlbflush.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index ed2317f19ec7..433eeaafe498 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -152,6 +152,15 @@ static inline void __native_flush_tlb_global(void)
 {
 	unsigned long flags;
 
+	if (static_cpu_has(X86_FEATURE_INVPCID)) {
+		/*
+		 * Using INVPCID is considerably faster than a pair of writes
+		 * to CR4 sandwiched inside an IRQ flag save/restore.
+		 */
+		invpcid_flush_all();
+		return;
+	}
+
 	/*
 	 * Read-modify-write to CR4 - protect it from preemption and
 	 * from interrupts. (Use the raw variant because this code can
-- 
2.16.2