linux-kernel - Re: 2.6.38.2 breaks suspend to disk

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Date:	Fri, 1 Apr 2011 19:14:55 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Yinghai Lu <yinghai@...nel.org>,
	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 Fri, 1 Apr 2011, H. Peter Anvin wrote:
> On 04/01/2011 09:06 AM, Yinghai Lu wrote:
> > Index: linux-2.6/arch/x86/kernel/setup.c
> > ===================================================================
> > --- linux-2.6.orig/arch/x86/kernel/setup.c
> > +++ linux-2.6/arch/x86/kernel/setup.c
> > @@ -294,10 +294,17 @@ static void __init init_gbpages(void)
> >      else
> >          direct_gbpages = 0;
> >  }
> > +static void __init store_mmu_cr4(void)
> > +{
> > +    mmu_cr4_features = read_cr4();
> > +}
> >  #else
> >  static inline void init_gbpages(void)
> >  {
> >  }
> > +static void __init store_mmu_cr4(void)
> > +{
> > +}
> >  static void __init cleanup_highmap(void)
> >  {
> >  }
> > @@ -929,6 +936,8 @@ void __init setup_arch(char **cmdline_p)
> >      /* max_pfn_mapped is updated here */
> >      max_low_pfn_mapped = init_memory_mapping(0, max_low_pfn<<PAGE_SHIFT);
> >      max_pfn_mapped = max_low_pfn_mapped;
> > +    /* after init_memory_mapping updating cr4*/
> > +    store_mmu_cr4();
> >  
> >  #ifdef CONFIG_X86_64
> >      if (max_pfn > max_low_pfn) {
> 
> This looks really, really, really wrong.
> 
> Why the heck should we save and restore CR4 only for x86-64?

AFAICT it has always been the case since the beginning of time (Initial
git repository build).
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