netdev - Re: [PATCH] x86/cpufeature: guard asm_volatile_goto usage with CC_HAVE_ASM

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Message-ID: <339b047f-7886-967b-08e0-703cd892de30@fb.com>
Date:   Sat, 14 Apr 2018 13:30:56 -0700
From:   Yonghong Song <yhs@...com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Alexei Starovoitov <ast@...com>
CC:     <mingo@...nel.org>, <daniel@...earbox.net>,
        <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
        <kernel-team@...com>, Thomas Gleixner <tglx@...utronix.de>,
        netdev <netdev@...r.kernel.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>
Subject: Re: [PATCH] x86/cpufeature: guard asm_volatile_goto usage with
 CC_HAVE_ASM_GOTO



On 4/14/18 3:11 AM, Peter Zijlstra wrote:
> On Fri, Apr 13, 2018 at 01:42:14PM -0700, Alexei Starovoitov wrote:
>> On 4/13/18 11:19 AM, Peter Zijlstra wrote:
>>> On Tue, Apr 10, 2018 at 02:28:04PM -0700, Alexei Starovoitov wrote:
>>>> Instead of
>>>> #ifdef CC_HAVE_ASM_GOTO
>>>> we can replace it with
>>>> #ifndef __BPF__
>>>> or some other name,
>>>
>>> I would prefer the BPF specific hack; otherwise we might be encouraging
>>> people to build the kernel proper without asm-goto.
>>>
>>
>> I don't understand this concern.
> 
> The thing is; this will be a (temporary) BPF specific hack. Hiding it
> behind something that looks 'normal' (CC_HAVE_ASM_GOTO) is just not
> right.

This is a fair concern. I will use a different macro and send v2 soon.
Thanks.