linux-kernel - Re: [PATCH v5 03/27] x86/fpu/xstate: Introduce XSAVES system states

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Date:   Wed, 17 Oct 2018 15:39:47 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Borislav Petkov <bp@...en8.de>, Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...capital.net>,
        Balbir Singh <bsingharora@...il.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>
Subject: Re: [PATCH v5 03/27] x86/fpu/xstate: Introduce XSAVES system states

On 10/17/18 3:41 AM, Borislav Petkov wrote:

>> @@ -702,6 +703,7 @@ static int init_xstate_size(void)
>>   */
>>  static void fpu__init_disable_system_xstate(void)
>>  {
>> +	xfeatures_mask_all = 0;
>>  	xfeatures_mask_user = 0;
>>  	cr4_clear_bits(X86_CR4_OSXSAVE);
>>  	fpu__xstate_clear_all_cpu_caps();
>> @@ -717,6 +719,8 @@ void __init fpu__init_system_xstate(void)
>>  	static int on_boot_cpu __initdata = 1;
>>  	int err;
>>  	int i;
>> +	u64 cpu_user_xfeatures_mask;
>> +	u64 cpu_system_xfeatures_mask;
> 
> Please sort function local variables declaration in a reverse christmas
> tree order:
> 
> 	<type> longest_variable_name;
> 	<type> shorter_var_name;
> 	<type> even_shorter;
> 	<type> i;

Hi,

Would you mind explaining this request? (requirement?)
Other than to say that it is the preference of some maintainers,
please say Why it is preferred.

and since the <type>s above won't typically be the same length,
it's not for variable name alignment, right?

thanks,
-- 
~Randy