linux-kernel - Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init

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Message-ID: <569FA333.7020401@zytor.com>
Date:	Wed, 20 Jan 2016 07:09:39 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...e.de>
Cc:	Brian Gerst <brgerst@...il.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after
 init

On 01/20/16 07:01, Borislav Petkov wrote:
> On Tue, Jan 19, 2016 at 08:02:01PM -0800, H. Peter Anvin wrote:
>> 	... "i" (1 << (bit & 7)),
>> 	    "m" (((const char *)boot_cpu_data->x86_capability)[bit >> 3]) ...
> 
> Nice!
> 
> I was going to do:
> 
> 		"i" (1 << (bit & 31)),
>                 "m" (((boot_cpu_data->x86_capability)[bit >> 5]))
> 

But then you're using testl and get long immediates.

(And the parentheses around boot_cpu_data->x86_capability are redundant.)

	-hpa