linux-kernel - Re: [PATCH 0/5] x86-64: Remove syscall instructions at fixed addresses

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Message-ID: <20110531131117.GB13888@elte.hu>
Date:	Tue, 31 May 2011 15:11:17 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Lutomirski <luto@....edu>
Cc:	Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Jan Beulich <JBeulich@...ell.com>
Subject: Re: [PATCH 0/5] x86-64: Remove syscall instructions at fixed
 addresses


* Andrew Lutomirski <luto@....edu> wrote:

> > You could start with picking the more compatible alternative 
> > instruction initially. I don't at all mind losing half a cycle of 
> > performance in that case ... this code should be secure first.
> 
> The more compatible one is mfence, which in some cases could (I 
> think) be a lot more than half a cycle.

I'd still suggest to do the mfence change now and remove the 
alternatives patching for now - if it's more than half a cycle then 
it sure will be implemented properly, right?

Thanks,

	Ingo
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