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Message-ID: <53A31EBD.8060708@zytor.com> Date: Thu, 19 Jun 2014 10:32:45 -0700 From: "H. Peter Anvin" <hpa@...or.com> To: Dave Hansen <dave.hansen@...el.com>, "Ren, Qiaowei" <qiaowei.ren@...el.com>, Borislav Petkov <bp@...en8.de> CC: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "x86@...nel.org" <x86@...nel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v6 07/10] x86, mpx: decode MPX instruction to get bound violation information 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@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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