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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_MUTT 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 6C5F5C43441 for ; Thu, 29 Nov 2018 14:35:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 34AD420863 for ; Thu, 29 Nov 2018 14:35:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="h6/ZuTs4" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 34AD420863 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=oracle.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 S2388941AbeK3BlY (ORCPT ); Thu, 29 Nov 2018 20:41:24 -0500 Received: from userp2120.oracle.com ([156.151.31.85]:48538 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729204AbeK3BlX (ORCPT ); Thu, 29 Nov 2018 20:41:23 -0500 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.22/8.16.0.22) with SMTP id wATEYFCd037857; Thu, 29 Nov 2018 14:35:16 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=corp-2018-07-02; bh=ufsnDxpStVvMCrqZSD2cNUP77nMk4wGNZjgcO+6p1E4=; b=h6/ZuTs4SAzotEbpgvc3VgY9GoB80GiHq8mbPvoyVvhggykIVAJUd8/qh93UqnJSotZB oyar+LNo+oogTWJnlDvTM5t7ftlVQk6lrZUu1TUKlUSfOLihDjUAUWgS7HuwQa2KejAv GA4n8TnktY7KSAVO+5HXG25aqMQPZLsL2pPcjpAKCWof67QE8RnbR19MsjigVqbdY8Sb rQIi46IeXfwDyXH+Q7EeR5kjA4RVCfeC7FTz8swrjAlLF9nIkbkzox9x9hJ+WToq62fb lF0AYFA6SXwUUQpUZ5ZTT5L03pOP9YHP2CSJjcdb87diFlPOA6HrzwC7YKBh+daygtOx 7w== Received: from userv0022.oracle.com (userv0022.oracle.com [156.151.31.74]) by userp2120.oracle.com with ESMTP id 2nxy9rgfxa-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 29 Nov 2018 14:35:15 +0000 Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userv0022.oracle.com (8.14.4/8.14.4) with ESMTP id wATEZEnu016619 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 29 Nov 2018 14:35:15 GMT Received: from abhmp0020.oracle.com (abhmp0020.oracle.com [141.146.116.26]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id wATEZDVq010016; Thu, 29 Nov 2018 14:35:13 GMT Received: from char.us.oracle.com (/10.152.32.25) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 29 Nov 2018 06:35:13 -0800 Received: by char.us.oracle.com (Postfix, from userid 1000) id 746B96A00FB; Thu, 29 Nov 2018 09:35:09 -0500 (EST) Date: Thu, 29 Nov 2018 09:35:09 -0500 From: Konrad Rzeszutek Wilk To: Thomas Gleixner Cc: LKML , x86@kernel.org, Peter Zijlstra , Andy Lutomirski , Linus Torvalds , Jiri Kosina , Tom Lendacky , Josh Poimboeuf , Andrea Arcangeli , David Woodhouse , Tim Chen , Andi Kleen , Dave Hansen , Casey Schaufler , Asit Mallick , Arjan van de Ven , Jon Masters , Waiman Long , Greg KH , Dave Stewart , Kees Cook Subject: Re: [patch V2 05/28] x86/speculation: Disable STIBP when enhanced IBRS is in use Message-ID: <20181129143509.GF32259@char.us.oracle.com> References: <20181125183328.318175777@linutronix.de> <20181125185003.966801480@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181125185003.966801480@linutronix.de> User-Agent: Mutt/1.8.3 (2017-05-23) X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9091 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1811290123 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Nov 25, 2018 at 07:33:33PM +0100, Thomas Gleixner wrote: > 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. Reviewed-by: Konrad Rzeszutek Wilk Thank you! > > 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 > >