linux-kernel - RE: [PATCH v9 09/12] x86, mpx: decode MPX instruction to get bound violation information

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Message-ID: <alpine.DEB.2.11.1410272135420.5308@nanos>
Date:	Mon, 27 Oct 2014 21:36:53 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	"Ren, Qiaowei" <qiaowei.ren@...el.com>
cc:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	"Hansen, Dave" <dave.hansen@...el.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
	"linux-mips@...ux-mips.org" <linux-mips@...ux-mips.org>
Subject: RE: [PATCH v9 09/12] x86, mpx: decode MPX instruction to get bound
 violation information

On Mon, 27 Oct 2014, Ren, Qiaowei wrote:
> On 2014-10-24, Thomas Gleixner wrote:
> > On Sun, 12 Oct 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.
> > 
> > My question still stands why using the existing decoder is an issue.
> > Performance is a complete non issue in case of a bounds violation and
> > the interface argument is just silly, really.
> > 
> 
> As hpa said, we only need to decode several mpx instructions
> including BNDCL/BNDCU, and general decoder looks like a little
> heavy. Peter, what do you think about it?

You're repeating yourself. Care to read the discussion about this from
the last round of review again?

Thanks,

	tglx
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