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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 46E28C43441 for ; Wed, 21 Nov 2018 20:20:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 11041214F1 for ; Wed, 21 Nov 2018 20:20:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 11041214F1 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de 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 S2389267AbeKVGx7 (ORCPT ); Thu, 22 Nov 2018 01:53:59 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:45190 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732500AbeKVGx6 (ORCPT ); Thu, 22 Nov 2018 01:53:58 -0500 Received: from localhost ([127.0.0.1] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1gPYwr-0000Fb-9u; Wed, 21 Nov 2018 21:18:09 +0100 Message-Id: <20181121201722.717439984@linutronix.de> User-Agent: quilt/0.65 Date: Wed, 21 Nov 2018 21:14:35 +0100 From: Thomas Gleixner To: LKML Cc: x86@kernel.org, Peter Zijlstra , Andy Lutomirski , Linus Torvalds , Jiri Kosina , Tom Lendacky , Josh Poimboeuf , Andrea Arcangeli , David Woodhouse , Andi Kleen , Dave Hansen , Casey Schaufler , Asit Mallick , Arjan van de Ven , Jon Masters , Waiman Long , Greg KH , Dave Stewart , Kees Cook , Tim Chen Subject: [patch 05/24] x86/speculation: Disable STIBP when enhanced IBRS is in use References: <20181121201430.559770965@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline; filename=x86-speculation-Disable-STIBP-when-enhanced-IBRS-is-in-use.patch Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Tim Chen If enhanced IBRS is active, STIBP is redundant for mitigating Spectre v2 user space exploits from hyperthread sibling. Disable STIBP when enhanced IBRS is used. Signed-off-by: Tim Chen Signed-off-by: Thomas Gleixner --- arch/x86/kernel/cpu/bugs.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -321,6 +321,10 @@ static bool stibp_needed(void) if (spectre_v2_enabled == SPECTRE_V2_NONE) return false; + /* Enhanced IBRS makes using STIBP unnecessary. */ + if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED) + return false; + if (!boot_cpu_has(X86_FEATURE_STIBP)) return false; @@ -846,6 +850,9 @@ 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