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 39773C54E8E for ; Mon, 11 May 2020 04:53:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 041AD2495A for ; Mon, 11 May 2020 04:53:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589172814; bh=u4mtq4oc2YFCohhLV9L1ke8AzlV9vHB9ppjZwfyugSc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=H0tCrx49pCAsWiCOuv5l6TgVQd3OPxHK4ks/vnvqgXzxxQJRW/tC0cCAXsPDYGdQV OS2R2eVV9WIYB+CcaJ/Ww4xWzu5tOrOHN/Gt/UpLLVq1HFcRLh63p1WcYhiR9eT+EI 1OmrpByB/6HpMUFrMCYClYDulMw6oNKXE9LJ6TCg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728379AbgEKExc (ORCPT ); Mon, 11 May 2020 00:53:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:37228 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728209AbgEKExb (ORCPT ); Mon, 11 May 2020 00:53:31 -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 DED2F24955; Mon, 11 May 2020 04:53:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589172811; bh=u4mtq4oc2YFCohhLV9L1ke8AzlV9vHB9ppjZwfyugSc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=N4iHGzcnuki8Fmmq8eCPl//ClO9NAzyOcOXMqzDMPj9xVAhMCNWn43Eq1jSgmFK9U uFbSuNOZTH/IC6TQ2jBIk81hoFP9s2jE3n++IhdOgdDHvje5HzjC5/zqllVkDzw5+e 2Y2rfihbOmqnnCBPXIRod1vQMUbFUty39tR8XNP4= 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 v12 03/18] x86/cpu: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Date: Mon, 11 May 2020 00:52:56 -0400 Message-Id: <20200511045311.4785-4-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200511045311.4785-1-sashal@kernel.org> References: <20200511045311.4785-1-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 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 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 | 24 +++++++++++++++++++ 2 files changed, 27 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 7bc83f3d9bdfe..af3aaade195b8 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3033,6 +3033,9 @@ 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 bed0cb83fe245..4224760c74e27 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -418,6 +418,22 @@ 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) +{ + unsafe_fsgsbase = true; + return 1; +} +__setup("unsafe_fsgsbase", setup_unsafe_fsgsbase); + /* * Protection Keys are not available in 32-bit mode. */ @@ -1478,6 +1494,14 @@ 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." -- 2.20.1