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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 D3C5DC47247 for ; Sat, 9 May 2020 17:37:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B5C712192A for ; Sat, 9 May 2020 17:37:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589045849; bh=EE4RUFzGtBnUhpN/W6GdiN9XdyqkBSLW/UwtcHAmuGs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=nbAI8tW4U98A33GtK443sgm2IwsgCOobCy5SWYP9bIpxzMqBJ0Mvx7ykRGLxnvQk4 0wAYu09pHBqNQ07LB+8pAiRt17372difr/ngQsxzHDnSiXOdoKE024WZe1HvtbpV5j vaJaoN/w6PwZW+MTbfxgMT13XuWA+qXG65rlyWDA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728689AbgEIRh2 (ORCPT ); Sat, 9 May 2020 13:37:28 -0400 Received: from mail.kernel.org ([198.145.29.99]:54736 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728638AbgEIRhX (ORCPT ); Sat, 9 May 2020 13:37:23 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1D44124965; Sat, 9 May 2020 17:37:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589045842; bh=EE4RUFzGtBnUhpN/W6GdiN9XdyqkBSLW/UwtcHAmuGs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ErOaAI9xXdbxRQHukIIvPYbwIX6HCsKNCnvQvm1C/qbyJnLLNihJQ0LezB6d2Wrn7 YE/dKY1RqWN7Aj+n3MKmjdkfbIcRd+HhucNHY39hkWl06i75b00xK50TuGQXgW8qgh esvtLDULsBmb9ZjhotrOBvLov3dKiQQwD8OZ/EAM= From: Sasha Levin To: linux-kernel@vger.kernel.org, tglx@linutronix.de, bp@alien8.de, luto@kernel.org Cc: hpa@zytor.com, dave.hansen@intel.com, tony.luck@intel.com, ak@linux.intel.com, ravi.v.shankar@intel.com, chang.seok.bae@intel.com, Sasha Levin Subject: [PATCH v11 16/18] x86/fsgsbase/64: Enable FSGSBASE on 64bit by default and add a chicken bit Date: Sat, 9 May 2020 13:36:53 -0400 Message-Id: <20200509173655.13977-17-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200509173655.13977-1-sashal@kernel.org> References: <20200509173655.13977-1-sashal@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andy Lutomirski Now that FSGSBASE is fully supported, remove unsafe_fsgsbase, enable FSGSBASE by default, and add nofsgsbase to disable it. While this changes userspace visible ABI, we could not find a project that would be affected by this. Few projects were contacted for input and ack: - 5-level EPT: http://lkml.kernel.org/r/9ddf602b-6c8b-8c1e-ab46-07ed12366593@redhat.com - rr: https://mail.mozilla.org/pipermail/rr-dev/2018-March/000616.html - CRIU: https://lists.openvz.org/pipermail/criu/2018-March/040654.html Signed-off-by: Andy Lutomirski Signed-off-by: Chang S. Bae Signed-off-by: Sasha Levin Reviewed-by: Tony Luck Cc: Thomas Gleixner Cc: Borislav Petkov Cc: Andy Lutomirski Cc: H. Peter Anvin Cc: Dave Hansen Cc: Tony Luck Cc: Andi Kleen --- .../admin-guide/kernel-parameters.txt | 3 +- arch/x86/kernel/cpu/common.c | 32 ++++++++----------- 2 files changed, 15 insertions(+), 20 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index af3aaade195b8..1924845c879c2 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3033,8 +3033,7 @@ 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. + nofsgsbase [X86] Disables FSGSBASE instructions. no_console_suspend [HW] Never suspend the console diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 4224760c74e27..0d480cbadc7dc 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -418,21 +418,21 @@ static void __init setup_cr_pinning(void) static_key_enable(&cr_pinning.key); } -/* - * 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) +static __init int x86_nofsgsbase_setup(char *arg) { - unsafe_fsgsbase = true; + /* Require an exact match without trailing characters. */ + if (strlen(arg)) + return 0; + + /* Do not emit a message if the feature is not present. */ + if (!boot_cpu_has(X86_FEATURE_FSGSBASE)) + return 1; + + setup_clear_cpu_cap(X86_FEATURE_FSGSBASE); + pr_info("FSGSBASE disabled via kernel command line\n"); return 1; } -__setup("unsafe_fsgsbase", setup_unsafe_fsgsbase); +__setup("nofsgsbase", x86_nofsgsbase_setup); /* * Protection Keys are not available in 32-bit mode. @@ -1495,12 +1495,8 @@ static void identify_cpu(struct cpuinfo_x86 *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); - } + if (cpu_has(c, X86_FEATURE_FSGSBASE)) + cr4_set_bits(X86_CR4_FSGSBASE); /* * The vendor-specific functions might have changed features. -- 2.20.1