From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.8 required=3.0 tests=DATE_IN_PAST_06_12, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AF030C04AAB for ; Wed, 8 May 2019 17:04:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8802F21530 for ; Wed, 8 May 2019 17:04:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729150AbfEHREM (ORCPT ); Wed, 8 May 2019 13:04:12 -0400 Received: from mga03.intel.com ([134.134.136.65]:5319 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728963AbfEHRDE (ORCPT ); Wed, 8 May 2019 13:03:04 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 08 May 2019 10:03:03 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,446,1549958400"; d="scan'208";a="169697556" Received: from chang-linux-3.sc.intel.com ([172.25.66.171]) by fmsmga002.fm.intel.com with ESMTP; 08 May 2019 10:03:02 -0700 From: "Chang S. Bae" To: Andy Lutomirski , Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , Andi Kleen Cc: Ravi Shankar , "Chang S . Bae" , LKML , Andrew Morton , Randy Dunlap Subject: [PATCH v7 03/18] x86/fsgsbase/64: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Date: Wed, 8 May 2019 03:02:18 -0700 Message-Id: <1557309753-24073-4-git-send-email-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1557309753-24073-1-git-send-email-chang.seok.bae@intel.com> References: <1557309753-24073-1-git-send-email-chang.seok.bae@intel.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andy Lutomirski This is temporary. It will allow the next few patches to be tested incrementally. Setting unsafe_fsgsbase is a root hole. Don't do it. Signed-off-by: Andy Lutomirski Signed-off-by: Chang S. Bae Reviewed-by: Andi Kleen Reviewed-by: Andy Lutomirski Cc: Thomas Gleixner Cc: Ingo Molnar Cc: H. Peter Anvin Cc: Andrew Morton Cc: Randy Dunlap --- Documentation/admin-guide/kernel-parameters.txt | 3 +++ arch/x86/kernel/cpu/common.c | 24 ++++++++++++++++++++++++ 2 files changed, 27 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index fd03e2b..7fe1da0 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2827,6 +2827,9 @@ no5lvl [X86-64] Disable 5-level paging mode. Forces kernel to use 4-level paging instead. + unsafe_fsgsbase [X86] Allow FSGSBASE instructions. This will be + replaced with a nofsgsbase flag. + no_console_suspend [HW] Never suspend the console Disable suspending of consoles during suspend and diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 8739bdf..5743cb9 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -366,6 +366,22 @@ static __always_inline void setup_umip(struct cpuinfo_x86 *c) } /* + * Temporary hack: FSGSBASE is unsafe until a few kernel code paths are + * updated. This allows us to get the kernel ready incrementally. + * + * Once all the pieces are in place, these will go away and be replaced with + * a nofsgsbase chicken flag. + */ +static bool unsafe_fsgsbase; + +static __init int setup_unsafe_fsgsbase(char *arg) +{ + unsafe_fsgsbase = true; + return 1; +} +__setup("unsafe_fsgsbase", setup_unsafe_fsgsbase); + +/* * Protection Keys are not available in 32-bit mode. */ static bool pku_disabled; @@ -1344,6 +1360,14 @@ static void identify_cpu(struct cpuinfo_x86 *c) setup_smap(c); setup_umip(c); + /* Enable FSGSBASE instructions if available. */ + if (cpu_has(c, X86_FEATURE_FSGSBASE)) { + if (unsafe_fsgsbase) + cr4_set_bits(X86_CR4_FSGSBASE); + else + clear_cpu_cap(c, X86_FEATURE_FSGSBASE); + } + /* * The vendor-specific functions might have changed features. * Now we do "generic changes." -- 2.7.4