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 1CBABC07E85 for ; Sat, 17 Nov 2018 02:27:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D57F62075B for ; Sat, 17 Nov 2018 02:27:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D57F62075B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731007AbeKQMme (ORCPT ); Sat, 17 Nov 2018 07:42:34 -0500 Received: from mga14.intel.com ([192.55.52.115]:45898 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727116AbeKQMme (ORCPT ); Sat, 17 Nov 2018 07:42:34 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 16 Nov 2018 18:27:38 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,242,1539673200"; d="scan'208";a="281852592" Received: from skl-02.jf.intel.com ([10.54.74.62]) by fmsmga006.fm.intel.com with ESMTP; 16 Nov 2018 18:27:38 -0800 From: Tim Chen To: Jiri Kosina , Thomas Gleixner Cc: Tim Chen , Tom Lendacky , Ingo Molnar , Peter Zijlstra , Josh Poimboeuf , Andrea Arcangeli , David Woodhouse , Andi Kleen , Dave Hansen , Casey Schaufler , Asit Mallick , Arjan van de Ven , Jon Masters , Waiman Long , linux-kernel@vger.kernel.org, x86@kernel.org Subject: [Patch v5 05/16] x86/speculation: Disable STIBP when enhanced IBRS is in use Date: Fri, 16 Nov 2018 17:53:48 -0800 Message-Id: <0904dd3f2fe7868954cd18c560817457918c9fd2.1542418937.git.tim.c.chen@linux.intel.com> X-Mailer: git-send-email 2.9.4 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If enhanced IBRS is engaged, STIBP is redundant in mitigating Spectre v2 user space exploits from hyperthread sibling. Disable STIBP when enhanced IBRS is used. Signed-off-by: Tim Chen --- arch/x86/kernel/cpu/bugs.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 3a6f13b..5c0eb2f 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -325,9 +325,17 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void) static bool stibp_needed(void) { + /* + * Determine if STIBP should be always on. + * Using enhanced IBRS makes using STIBP unnecessary. + */ + if (spectre_v2_enabled == SPECTRE_V2_NONE) return false; + if (static_cpu_has(X86_FEATURE_USE_IBRS_ENHANCED)) + return false; + if (!boot_cpu_has(X86_FEATURE_STIBP)) return false; @@ -856,6 +864,9 @@ static ssize_t l1tf_show_state(char *buf) static char *stibp_state(void) { + if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED) + return ""; + if (x86_spec_ctrl_base & SPEC_CTRL_STIBP) return ", STIBP"; else -- 2.9.4