linux-kernel - Re: [PATCH] [RFC] Save/restore MISC

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Message-ID: <4C0D2BFB.2090200@zytor.com>
Date:	Mon, 07 Jun 2010 10:27:23 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ondrej Zary <linux@...nbow-software.org>
CC:	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [PATCH] [RFC] Save/restore MISC_ENABLE register

On 06/07/2010 09:14 AM, Ondrej Zary wrote:
> Save/restore MISC_ENABLE register on suspend/resume.
> This fixes OOPS (invalid opcode) on resume from STR on Asus P4P800-VM, which
> wakes up with MWAIT disabled.
> 
> Is this a correct thing to do? Is it OK on x86_64?

This MSR isn't available on all processors, and thus cannot be saved and
restored unconditionally like this.  On the save path, one can use
rdmsr_safe(); on the wakeup path it's not clear to me it is safe to do
so, so it would be better to save a presence flag on the save path and
conditionalize the write.

	-hpa
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