Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934032AbaFSRdl (ORCPT ); Thu, 19 Jun 2014 13:33:41 -0400 Received: from terminus.zytor.com ([198.137.202.10]:60358 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932295AbaFSRdj (ORCPT ); Thu, 19 Jun 2014 13:33:39 -0400 Message-ID: <53A31EBD.8060708@zytor.com> Date: Thu, 19 Jun 2014 10:32:45 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Dave Hansen , "Ren, Qiaowei" , Borislav Petkov CC: Thomas Gleixner , Ingo Molnar , "x86@kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v6 07/10] x86, mpx: decode MPX instruction to get bound violation information References: <1403084656-27284-1-git-send-email-qiaowei.ren@intel.com> <1403084656-27284-8-git-send-email-qiaowei.ren@intel.com> <20140618100745.GB24419@pd.tnic> <9E0BE1322F2F2246BD820DA9FC397ADE016A3BAA@shsmsx102.ccr.corp.intel.com> <20140619062824.GB22025@pd.tnic> <9E0BE1322F2F2246BD820DA9FC397ADE016A3F75@shsmsx102.ccr.corp.intel.com> <53A3181F.9070005@intel.com> In-Reply-To: <53A3181F.9070005@intel.com> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/19/2014 10:04 AM, Dave Hansen wrote: > > Could you please support this position with some data? I'm a bit > skeptical that instruction decoding is going to be a > performance-critical path. > > I also don't see the extra field that you talked about in the previous > thread? What's the extra field? I see a 'limit' vs. 'length', but you > don't use 'length' at all, so I think you can use it instead, or at > least union it. > > I've taken a quick stab at trying to consolidate things. I think I may > have screwed up this: > > insn->limit = MAX_MPX_INSN_SIZE - bytes; > > Qiaowei, is there anything fundamentally broken with what I've got here? > So I encouraged Qiaowei to do a limited special-purpose decoder, simply because the glue to use the generic decoder was almost as large. I am overall not a huge fan of using the generic decoder in constrained situation, because the generic decoder is very heavyweight not just in terms of performance but in terms of interface -- because it has to. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/