linux-kernel - Re: 2.6.38.2 breaks suspend to disk

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Message-ID: <4D96695D.7020706@kernel.org>
Date:	Fri, 01 Apr 2011 17:10:05 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Ingo Molnar <mingo@...hat.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Michael Leun <lkml20101129@...ton.leun.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Mike Pagano <mpagano@...too.org>
Subject: Re: 2.6.38.2 breaks suspend to disk

On 04/01/2011 04:12 PM, H. Peter Anvin wrote:
> On 04/01/2011 04:04 PM, Yinghai Lu wrote:
>> On 04/01/2011 02:42 PM, H. Peter Anvin wrote:
>>>
>>> And why on Earth is it worth saving a couple of instructions (and
>>> introducing code ugliness and a more complex testing matrix) in the case
>>> when it is not?
>>
>> Please check this one, it moves storing mmu_cr4 to arch_prepare_suspend.
>>
>
> You keep moving things around instead of answering the question.  It
> might be the right thing to do, but I would like an answer why, in your
> opinion, the easy way isn't feasible.

want to find right place to read back cr4 for hibernation/resume.

it is one time using, so we could just read back one time at last and avoid touching it
inset/clear_in_cr4.

>
> For suspend/resume, the right thing really is just to save CR4 like any
> other processor register.

not sure why mmu_cr4_features get overloaded. maybe power guys want to save one variable instead of using restore_rc4.

Thanks

Yinghai
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