Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4F2F1C38142 for ; Tue, 31 Jan 2023 22:48:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231524AbjAaWsN (ORCPT ); Tue, 31 Jan 2023 17:48:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40958 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232068AbjAaWsJ (ORCPT ); Tue, 31 Jan 2023 17:48:09 -0500 Received: from mga06.intel.com (mga06b.intel.com [134.134.136.31]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E262A274BC; Tue, 31 Jan 2023 14:48:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1675205287; x=1706741287; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=s/SDjQxQzEEm/Q6iuxlrqRAomix1+H5xLpivUae6uhw=; b=nCLLLK8h+PD8hLgJX/vLeDoJg3a3Gzums6w+f3K+n8O9o9GALorvkzS8 ZYQH3nAHghfu5zyymcEaJxFql/OqheII1mcrT8iG66KQWvchxSiwwD56w TMmJcqP7EPjKRJe8stR0yyPLN2FgBHVzJ3F0PtNaR6SUjbTLe35jQEpui xehbKCx2e3e83O7UcPLif3mMkiv6Uf5ADEoITV0GOzLhIaxs0e+3ooNSk BqqvoKN38bwFzlTWpwXH5CLLfIlyy/DIoRRIpuEB8KwKtDrk8ZXlBOkMa aCuhp+swpMAp331EiXlYy35NhFnQvaZulgRSoB1o8SjpsSh/ZuJH5pG9S A==; X-IronPort-AV: E=McAfee;i="6500,9779,10607"; a="390349000" X-IronPort-AV: E=Sophos;i="5.97,261,1669104000"; d="scan'208";a="390349000" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Jan 2023 14:48:07 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10607"; a="773175008" X-IronPort-AV: E=Sophos;i="5.97,261,1669104000"; d="scan'208";a="773175008" Received: from bdoolin-mobl1.amr.corp.intel.com (HELO [10.209.125.63]) ([10.209.125.63]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Jan 2023 14:48:06 -0800 Message-ID: <16e3217b-1561-51ea-7514-014e27240402@intel.com> Date: Tue, 31 Jan 2023 14:48:05 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.1 Subject: Re: [PATCH] x86: enable Data Operand Independent Timing Mode Content-Language: en-US To: Eric Biggers Cc: Jann Horn , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , x86@kernel.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, Peter Zijlstra , Roxana Bradescu , Adam Langley , Ard Biesheuvel , "Jason A . Donenfeld" References: <20230125012801.362496-1-ebiggers@kernel.org> <14506678-918f-81e1-2c26-2b347ff50701@intel.com> <394c92e2-a9aa-37e1-7a34-d7569ac844fd@intel.com> <8b2771ce-9cfa-54cc-de6b-e80ce7af0a93@intel.com> From: Dave Hansen In-Reply-To: <8b2771ce-9cfa-54cc-de6b-e80ce7af0a93@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We've been talking about this inside Intel. Suffice to say that DOITM was not designed to be turned on all the time. If software turns it on all the time, it won't accomplish what it was designed to do. The _most_ likely thing that's going to happen is that DOITM gets redefined to be much more limited in scope. The current DOITM architecture is very broad, but the implementations have much more limited effects. This means that the architecture can probably be constrained and still match the hardware that's out there today. That's pure speculation (ha!) on my part. I think we should hold off on merging any DOITM patches until the dust settles. As far as I know, there is no pressing practical reason to apply something urgently. Any objections?