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

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Message-ID: <544F307D.7090701@intel.com>
Date:	Tue, 28 Oct 2014 13:58:21 +0800
From:	Ren Qiaowei <qiaowei.ren@...el.com>
To:	Thomas Gleixner <tglx@...utronix.de>
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 10/28/2014 04:36 AM, Thomas Gleixner wrote:
> 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?
>

Ok. I will go through it again. Thanks.

- Qiaowei
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