Received: by 10.223.148.5 with SMTP id 5csp7762434wrq; Thu, 18 Jan 2018 09:09:28 -0800 (PST) X-Google-Smtp-Source: ACJfBotgXCXVZYPhsIbILTxZ3K+L2XtUmOf17RFWHqbGsNWYB3QgHdfmnXejCibLrbwkjxfYBoH3 X-Received: by 10.98.66.67 with SMTP id p64mr36215640pfa.227.1516295368428; Thu, 18 Jan 2018 09:09:28 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1516295368; cv=none; d=google.com; s=arc-20160816; b=r6uq8FeOooFY2ksitKO3CSoXY6SwaCnN+UA1YUECwjBRFVDPfN5vMzgYOcWovb5jRa msy/4l07/JYAgwpXXkX909qxVLXbm8OkdVVrsOyyt+BoyFGZcvfnXeGzIZVhZ6jJy0e7 cqtY8ViUDvpre1nsU+LaGAaYXXPFTANY1RM/kbo2ZQCvtMww7Or/INPxLe9bVkON6PL9 XqcDgfVVLADvEMetyOe2n3LVqJl6II+Eo3ZJ/jFVxYv+6y8ixVlnC30Qs/Q9OFsHmPOj BLHsuqUt+7boZMJitxnW6aJCFQKcJmQzCvES9TbGNta5ZkfrGTwFh/oPkBKCo1jV1tQL q9Ng== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:content-transfer-encoding :content-language:in-reply-to:mime-version:user-agent:date :message-id:from:cc:references:to:subject:arc-authentication-results; bh=0iowQxjUxrO28EezWWNRQZFh6WI7236vpKoSCpcbdIs=; b=ImoYPGV0lxnhff1LZageydCmdkIUn2ZijoLgaimeaIU7fq52lySOnzVf6y9JqadrtJ efwhOoz7gjV3fzMVh/NGUshN/qGtH5FlKfToTYSxlY3rBTszMxndpT4qRbpW2JwVPtuW dAWM02bcz4Om8qFGKKU+6jaFV92dZ2OD+YI24AA8rUZItWWELV/pYXA4drOXDO7/WNTv cbKFynIbZ6ue7KD9YavsfuW+FWkyg/nBpSQL/eE/GjLF1BuJMpv2M53+hVk/4BHCSw9S Z9sDpULEiMAI9hCqv+5At3XudoeZLEEDbk5Gv3/DH9Lmt4f4QN8da0+IEtfc1/pFcFK3 vgag== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id p71si7289688pfl.404.2018.01.18.09.09.13; Thu, 18 Jan 2018 09:09:28 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755003AbeARRIR (ORCPT + 99 others); Thu, 18 Jan 2018 12:08:17 -0500 Received: from mga02.intel.com ([134.134.136.20]:12329 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750841AbeARRIQ (ORCPT ); Thu, 18 Jan 2018 12:08:16 -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 orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 18 Jan 2018 09:08:05 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.46,378,1511856000"; d="scan'208";a="196794256" Received: from ray.jf.intel.com (HELO [10.24.8.174]) ([10.24.8.174]) by fmsmga006.fm.intel.com with ESMTP; 18 Jan 2018 09:08:04 -0800 Subject: Re: [PATCH 23/35] x86/speculation: Add basic speculation control code To: Josh Poimboeuf , Peter Zijlstra References: <20180118134800.711245485@infradead.org> <20180118140152.830682032@infradead.org> <20180118163745.t5nmwdr53wjsl7o5@treble> Cc: David Woodhouse , Thomas Gleixner , linux-kernel@vger.kernel.org, Ashok Raj , Tim Chen , Andy Lutomirski , Linus Torvalds , Greg KH , Andrea Arcangeli , Andi Kleen , Arjan Van De Ven , Dan Williams , Paolo Bonzini , Jun Nakajima , Asit Mallick , Jason Baron From: Dave Hansen Message-ID: <73a5735a-6a5b-0e0f-1f0b-e7cd955880d2@intel.com> Date: Thu, 18 Jan 2018 09:08:02 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 In-Reply-To: <20180118163745.t5nmwdr53wjsl7o5@treble> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/18/2018 08:37 AM, Josh Poimboeuf wrote: >> >> --- a/Documentation/admin-guide/kernel-parameters.txt >> +++ b/Documentation/admin-guide/kernel-parameters.txt >> @@ -3932,6 +3932,7 @@ >> retpoline - replace indirect branches >> retpoline,generic - google's original retpoline >> retpoline,amd - AMD-specific minimal thunk >> + ibrs - Intel: Indirect Branch Restricted Speculation > Are there plans to add spectre_v2=ibrs_always to prevent SMT-based > attacks? What does "ibrs_always" mean to you? There is a second bit in the MSR (STIBP) that is intended to keep hyperthreads from influencing each-other. That is behavior is implicit when IBRS is enabled. I think ibrs_always *should* probably be kept to refer to the future CPUs that can safely leave IBRS enabled all the time.