linux-kernel - Re: [PATCH urgent] x86: Save cr4 to mmu_cr4

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Date:	Wed, 6 Apr 2011 06:34:12 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"yinghai@...nel.org" <yinghai@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Greg KH <gregkh@...e.de>,
	"lkml20101129@...ton.leun.net" <lkml20101129@...ton.leun.net>,
	stable kernel team <stable@...nel.org>,
	Jeremy Fitzhardinge <Jeremy.Fitzhardinge@...rix.com>
Subject: Re: [PATCH urgent] x86: Save cr4 to mmu_cr4_features at boot time

On Wednesday, April 06, 2011, H. Peter Anvin wrote:
> On 04/04/2011 11:43 PM, Rafael J. Wysocki wrote:
> > On Tuesday, April 05, 2011, H. Peter Anvin wrote:
> >> On 04/04/2011 11:29 PM, Rafael J. Wysocki wrote:
> >>>>
> >>>> Peter very consciously did not mark the fix for this commit as -stable 
> >>>> material. It was ineligible for -stable for multiple reasons: it by no means 
> >>>> fixed a 2.6.39 regression and the fix was literally just a few days old.
> >>>
> >>> Has this issue been resolved in the mainline, BTW?
> >>>
> >>
> >> Just to refresh my memory... is this an issue in mainline, or is it only
> >> a problem in the backport (I'm wondering if the trampoline unification
> >> patches might have accidentally solved the issue)?
> > 
> > 
> > The problem is in mainline too, please fix ASAP.
> > 
> 
> For the suspend/resume case this seems like the sanest way to fix it in
> my opinion.  However, I am a bit concerned since I'm still not sure
> we're programming registers in the correct order, that is:
> 
> MISC_ENABLE -> EFER -> cr4 -> cr3 -> cr0
> 
> I will look at this issue later this evening, but I wanted your opinion
> on it.

Do you mean during resume?

I think we can try to make the ordering more appropriate, but I'm not really
sure it would be a good idea to do that in the same patch.  Probably not.

Also, our current ordering has never been reported to cause problems to anyone.

Thanks,
Rafael
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