linux-kernel - Re: [PATCH v8 07/10] x86, mpx: decode MPX instruction to get bound violation information

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Date:	Thu, 11 Sep 2014 15:35:29 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Dave Hansen <dave.hansen@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Qiaowei Ren <qiaowei.ren@...el.com>
CC:	Ingo Molnar <mingo@...hat.com>, x86@...nel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 07/10] x86, mpx: decode MPX instruction to get bound
 violation information

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

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