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=-9.0 required=3.0 tests=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 DFE56C43381 for ; Fri, 15 Mar 2019 20:08:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B5811218A1 for ; Fri, 15 Mar 2019 20:08:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727124AbfCOUID (ORCPT ); Fri, 15 Mar 2019 16:08:03 -0400 Received: from mga01.intel.com ([192.55.52.88]:22894 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726314AbfCOUHA (ORCPT ); Fri, 15 Mar 2019 16:07:00 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 15 Mar 2019 13:07:00 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,483,1544515200"; d="scan'208";a="307617683" Received: from chang-linux-3.sc.intel.com ([143.183.85.65]) by orsmga005.jf.intel.com with ESMTP; 15 Mar 2019 13:06:59 -0700 From: "Chang S. Bae" To: Thomas Gleixner , Ingo Molnar , Andy Lutomirski , "H . Peter Anvin" , Andi Kleen Cc: Ravi Shankar , "Chang S . Bae" , LKML , Andrew Morton , Randy Dunlap Subject: [RESEND PATCH v6 01/12] x86/fsgsbase/64: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Date: Fri, 15 Mar 2019 13:06:34 -0700 Message-Id: <1552680405-5265-2-git-send-email-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1552680405-5265-1-git-send-email-chang.seok.bae@intel.com> References: <1552680405-5265-1-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 --- .../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 cf8f5877d85f..b6ed956a78ab 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2765,6 +2765,9 @@ 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 cb28e98a0659..40a2f60e7251 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -365,6 +365,22 @@ static __always_inline void setup_umip(struct cpuinfo_x86 *c) cr4_clear_bits(X86_CR4_UMIP); } +/* + * 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. */ @@ -1352,6 +1368,14 @@ 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." -- 2.19.1