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Date: Thu, 11 Sep 2014 15:35:29 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Dave Hansen <dave.hansen@intel.com>, Thomas Gleixner <tglx@linutronix.de>,
        Qiaowei Ren <qiaowei.ren@intel.com>
CC: Ingo Molnar <mingo@redhat.com>, x86@kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v8 07/10] x86, mpx: decode MPX instruction to get bound
 violation information
References: <1410425210-24789-1-git-send-email-qiaowei.ren@intel.com> <1410425210-24789-8-git-send-email-qiaowei.ren@intel.com> <alpine.DEB.2.10.1409120015030.4178@nanos> <5412230A.6090805@intel.com>
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On 09/11/2014 03:32 PM, Dave Hansen wrote:
> On 09/11/2014 03:18 PM, Thomas Gleixner wrote:
>> On Thu, 11 Sep 2014, Qiaowei Ren wrote:
>>> This patch sets bound violation fields of siginfo struct in #BR
>>> exception handler by decoding the user instruction and constructing
>>> the faulting pointer.
>>>
>>> This patch does't use the generic decoder, and implements a limited
>>> special-purpose decoder to decode MPX instructions, simply because the
>>> generic decoder is very heavyweight not just in terms of performance
>>> but in terms of interface -- because it has to.
>>
>> And why is that an argument to add another special purpose decoder?
> 
> Peter asked for it to be done this way specifically:
> 
> 	https://lkml.org/lkml/2014/6/19/411
> 

Specifically because marshaling the data in and out of the generic
decoder was more complex than a special-purpose decoder.

	-hpa