linux-kernel - Re: [PATCH v7 03/10] x86, mpx: add macro cpu_has

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Message-ID: <53D08FA4.4030700@intel.com>
Date:	Wed, 23 Jul 2014 21:46:28 -0700
From:	Dave Hansen <dave.hansen@...el.com>
To:	"Ren, Qiaowei" <qiaowei.ren@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>
CC:	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH v7 03/10] x86, mpx: add macro cpu_has_mpx

On 07/23/2014 05:56 PM, Ren, Qiaowei wrote:
> On 2014-07-24, Hansen, Dave wrote:
>> On 07/22/2014 07:35 PM, Ren, Qiaowei wrote:
>>> The checking about MPX feature should be as follow:
>>>
>>>         if (pcntxt_mask & XSTATE_EAGER) {
>>>                 if (eagerfpu == DISABLE) {
>>>                         pr_err("eagerfpu not present, disabling some
>> xstate features: 0x%llx\n",
>>>                                         pcntxt_mask &
>> XSTATE_EAGER);
>>>                         pcntxt_mask &= ~XSTATE_EAGER; } else { eagerfpu
>>>                         = ENABLE;
>>>                 }
>>>         }
>>> This patch was merged into kernel the ending of last year
>>> (https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/com
>>> mi
>>> t/?id=e7d820a5e549b3eb6c3f9467507566565646a669 )
>>
>> Should we be doing a clear_cpu_cap(X86_FEATURE_MPX) in here?
>> 
>> This isn't major, but I can't _ever_ imagine a user being able to 
>> track down why MPX is not working from this message. Should we
>> spruce it up somehow?
> 
> Maybe. If the error log "disabling some xstate features:" is changed
> to "disabling MPX xstate features:", do you think it is OK?

That's better.  Is it really disabling MPX, though?

And shouldn't we clear the cpu feature bit too?
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