Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753337AbdFUFYI (ORCPT ); Wed, 21 Jun 2017 01:24:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:55600 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753211AbdFUFW2 (ORCPT ); Wed, 21 Jun 2017 01:22:28 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 91D8423A24 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=luto@kernel.org From: Andy Lutomirski To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, Borislav Petkov , Linus Torvalds , Andrew Morton , Mel Gorman , "linux-mm@kvack.org" , Nadav Amit , Rik van Riel , Dave Hansen , Arjan van de Ven , Peter Zijlstra , Andy Lutomirski Subject: [PATCH v3 09/11] x86/mm: Add nopcid to turn off PCID Date: Tue, 20 Jun 2017 22:22:15 -0700 Message-Id: <17c3a4f2e16aa83cbfea8ca9957ce75efbcf7f95.1498022414.git.luto@kernel.org> X-Mailer: git-send-email 2.9.4 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 Content-Length: 1676 Lines: 53 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/admin-guide/kernel-parameters.txt | 2 ++ arch/x86/kernel/cpu/common.c | 18 ++++++++++++++++++ 2 files changed, 20 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 0f5c3b4347c6..aa385109ae58 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2648,6 +2648,8 @@ 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 c8b39870f33e..904485e7b230 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -168,6 +168,24 @@ 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 */ -- 2.9.4