From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756158AbcAHXPt (ORCPT ); Fri, 8 Jan 2016 18:15:49 -0500 Received: from mail.kernel.org ([198.145.29.136]:49723 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756111AbcAHXPq (ORCPT ); Fri, 8 Jan 2016 18:15:46 -0500 From: Andy Lutomirski To: x86@kernel.org, linux-kernel@vger.kernel.org Cc: Borislav Petkov , Brian Gerst , Dave Hansen , Linus Torvalds , Oleg Nesterov , "linux-mm@kvack.org" , Andy Lutomirski Subject: [RFC 07/13] x86/mm: Add nopcid to turn off PCID Date: Fri, 8 Jan 2016 15:15:25 -0800 Message-Id: <7752daf506becd3b36e768bd2561f562f64d9d16.1452294700.git.luto@kernel.org> X-Mailer: git-send-email 2.5.0 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The parameter is only present on x86_64 systems to save a few bytes, as PCID is always disabled on x86_32. Signed-off-by: Andy Lutomirski --- Documentation/kernel-parameters.txt | 2 ++ arch/x86/kernel/cpu/common.c | 18 ++++++++++++++++++ 2 files changed, 20 insertions(+) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index b34e55e00bae..2f61809706c5 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -2544,6 +2544,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted. nopat [X86] Disable PAT (page attribute table extension of pagetables) support. + nopcid [X86-64] Disable the PCID cpu feature. + norandmaps Don't use address space randomization. Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 48196980c1c7..7e1fc53a4ba5 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -162,6 +162,24 @@ static int __init x86_mpx_setup(char *s) } __setup("nompx", x86_mpx_setup); +#ifdef CONFIG_X86_64 +static int __init x86_pcid_setup(char *s) +{ + /* require an exact match without trailing characters */ + if (strlen(s)) + return 0; + + /* do not emit a message if the feature is not present */ + if (!boot_cpu_has(X86_FEATURE_PCID)) + return 1; + + setup_clear_cpu_cap(X86_FEATURE_PCID); + pr_info("nopcid: PCID feature disabled\n"); + return 1; +} +__setup("nopcid", x86_pcid_setup); +#endif + static int __init x86_noinvpcid_setup(char *s) { /* noinvpcid doesn't accept parameters */ -- 2.5.0