linux-kernel - [RFC 03/13] x86/mm: Add a noinvpcid option to turn off INVPCID

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Message-Id: <b41559f7b75e4574d7b6b30214ca57d0eabd39a7.1452294700.git.luto@kernel.org>
Date:	Fri,  8 Jan 2016 15:15:21 -0800
From:	Andy Lutomirski <luto@...nel.org>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Cc:	Borislav Petkov <bp@...en8.de>, Brian Gerst <brgerst@...il.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andy Lutomirski <luto@...nel.org>
Subject: [RFC 03/13] x86/mm: Add a noinvpcid option to turn off INVPCID

Signed-off-by: Andy Lutomirski <luto@...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 742f69d18fc8..b34e55e00bae 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2508,6 +2508,8 @@ 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 c2b7522cbf35..48196980c1c7 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;
-- 
2.5.0