From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 56173 invoked by alias); 14 Jan 2018 10:40:26 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 56164 invoked by uid 89); 14 Jan 2018 10:40:25 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-5.9 required=5.0 tests=AWL,BAYES_00,GIT_PATCH_2,KAM_LAZY_DOMAIN_SECURITY,T_RP_MATCHES_RCVD autolearn=ham version=3.3.2 spammy=H*f:sk:BN6PR12, H*i:sk:BN6PR12, Hx-languages-length:1429, HContent-Transfer-Encoding:8bit X-HELO: nikam.ms.mff.cuni.cz Received: from nikam.ms.mff.cuni.cz (HELO nikam.ms.mff.cuni.cz) (195.113.20.16) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Sun, 14 Jan 2018 10:40:23 +0000 Received: by nikam.ms.mff.cuni.cz (Postfix, from userid 16202) id 1D8A8541584; Sun, 14 Jan 2018 11:40:21 +0100 (CET) Date: Sun, 14 Jan 2018 10:45:00 -0000 From: Jan Hubicka To: "Kumar, Venkataramanan" Cc: "H.J. Lu" , "gcc-patches@gcc.gnu.org" , "Dharmakan, Rohit arul raj" , "Nagarajan, Muthu kumar raj" , "Uros Bizjak (ubizjak@gmail.com)" Subject: Re: [PATCH 0/5] x86: CVE-2017-5715, aka Spectre Message-ID: <20180114104020.GB62416@kam.mff.cuni.cz> References: <20180114033707.6297-1-hjl.tools@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-2 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-SW-Source: 2018-01/txt/msg01214.txt.bz2 > Hi HJ, > > > -----Original Message----- > > From: gcc-patches-owner@gcc.gnu.org [mailto:gcc-patches- > > owner@gcc.gnu.org] On Behalf Of H.J. Lu > > Sent: Sunday, January 14, 2018 9:07 AM > > To: gcc-patches@gcc.gnu.org > > Subject: [PATCH 0/5] x86: CVE-2017-5715, aka Spectre > > > > This set of patches for GCC 8 mitigates variant #2 of the speculative > > execution vulnerabilities on x86 processors identified by CVE-2017-5715, aka > > Spectre. They convert indirect branches and function returns to call and > > return thunks to avoid speculative execution via indirect call, jmp and ret. > > > > H.J. Lu (5): > > x86: Add -mindirect-branch= > > x86: Add -mfunction-return= > > x86: Add -mindirect-branch-register > > x86: Add 'V' register operand modifier > > x86: Disallow -mindirect-branch=/-mfunction-return= with > > -mcmodel=large > > Current set of patches don't seem to have any option to generate "lfence" as the loop filler in "retpoline",  which is required by AMD. > Can you please clarify the plan. We would like to get this checked-in GCC 8.  Since thunks are output as strings, it is easy to add the option on the top of patch #1 of the series. I do not fully understand the reason for choosing pause over lfence for Intel, but if we need to do both, we need to have command line option (and possibly attribute). What would be reasonable name for it? Honza