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

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Date:	Fri, 12 Sep 2014 00:18:15 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Qiaowei Ren <qiaowei.ren@...el.com>
cc:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...el.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 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?

If a bound violation happens it is completely irrelevant whether the
decoder is heavyweight or not.

So unless you come up with a convincing argument why the generic
decoder is the wrong place, this won't happen.

Thanks,

	tglx
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