linux-kernel - Re: [PATCH] x86: add missing verify

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Message-ID: <4E0E532C.2060807@zytor.com>
Date:	Fri, 01 Jul 2011 16:07:24 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Kees Cook <kees.cook@...onical.com>
CC:	linux-kernel@...r.kernel.org, Len Brown <len.brown@...el.com>,
	Pavel Machek <pavel@....cz>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	Pekka Enberg <penberg@...helsinki.fi>,
	Brian Gerst <brgerst@...il.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH] x86: add missing verify_cpu to 32bit wakeup

On 07/01/2011 03:36 PM, Kees Cook wrote:
>>
>> For S3, we should save/restore MISC_ENABLE instead... in fact, we
>> already save it, we just restore it too late.
> 
> Given that MISC_ENABLE may not be available for a given CPU, it seems that
> it's basically the same detection code as in verify_cpu() already. Since
> this bit is the only part that is needed that early, I think the patch is
> good the way it is (especially since it balances the 64bit path which
> already calls this logic). I don't think doing the full early MISC_ENABLE
> save/restore this early is worth it. Thoughts?
> 

We already save it, including if it exists, so we should just restore it
early, and then we don't have to do it again.

	-hpa

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