linux-kernel - [tip:x86/mm] x86/mm: Add a 'noinvpcid' boot option to turn off INVPCID

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Date:	Tue, 9 Feb 2016 08:07:52 -0800
From:	tip-bot for Andy Lutomirski <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	dave.hansen@...ux.intel.com, bp@...en8.de, luto@...nel.org,
	mingo@...nel.org, hpa@...or.com, tglx@...utronix.de,
	luto@...capital.net, aryabinin@...tuozzo.com, dvlasenk@...hat.com,
	bp@...e.de, peterz@...radead.org, torvalds@...ux-foundation.org,
	toshi.kani@...com, mcgrof@...e.com, oleg@...hat.com,
	brgerst@...il.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: [tip:x86/mm] x86/mm: Add a 'noinvpcid'
  boot option to turn off INVPCID

Commit-ID:  d12a72b844a49d4162f24cefdab30bed3f86730e
Gitweb:     http://git.kernel.org/tip/d12a72b844a49d4162f24cefdab30bed3f86730e
Author:     Andy Lutomirski <luto@...nel.org>
AuthorDate: Fri, 29 Jan 2016 11:42:58 -0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 9 Feb 2016 13:36:10 +0100

x86/mm: Add a 'noinvpcid' boot option to turn off INVPCID

This adds a chicken bit to turn off INVPCID in case something goes
wrong.  It's an early_param() because we do TLB flushes before we
parse __setup() parameters.

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/f586317ed1bc2b87aee652267e515b90051af385.1454096309.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 Documentation/kernel-parameters.txt |  2 ++
 arch/x86/kernel/cpu/common.c        | 16 ++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 551ecf0..e4c4d2a 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2566,6 +2566,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
 	nointroute	[IA-64]
 
+	noinvpcid	[X86] Disable the INVPCID cpu feature.
+
 	nojitter	[IA-64] Disables jitter checking for ITC timers.
 
 	no-kvmclock	[X86,KVM] Disable paravirtualized KVM clock driver
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 37830de..f4d0aa6 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -162,6 +162,22 @@ static int __init x86_mpx_setup(char *s)
 }
 __setup("nompx", x86_mpx_setup);
 
+static int __init x86_noinvpcid_setup(char *s)
+{
+	/* noinvpcid doesn't accept parameters */
+	if (s)
+		return -EINVAL;
+
+	/* do not emit a message if the feature is not present */
+	if (!boot_cpu_has(X86_FEATURE_INVPCID))
+		return 0;
+
+	setup_clear_cpu_cap(X86_FEATURE_INVPCID);
+	pr_info("noinvpcid: INVPCID feature disabled\n");
+	return 0;
+}
+early_param("noinvpcid", x86_noinvpcid_setup);
+
 #ifdef CONFIG_X86_32
 static int cachesize_override = -1;
 static int disable_x86_serial_nr = 1;