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

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Date:	Thu, 21 Jan 2016 15:36:12 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...e.de>
Cc:	Andy Lutomirski <luto@...capital.net>,
	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>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after
 init

On 01/21/16 14:56, Borislav Petkov wrote:
> 
> so this is silly: we're basically jumping after the JMP instruction
> itself. So that will be the case on !X86_BUG_SYSRET_SS_ATTRS CPUs.
> Still a two-byte and now even a useless JMP.
> 
> The right thing to do would be to generate a NOP simply.
> 

OK, so gcc isn't as clever as I thought.

	-hpa