linux-kernel - Re: 2.6.38.2 breaks suspend to disk

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Date:	Fri, 01 Apr 2011 09:06:37 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Ingo Molnar <mingo@...hat.com>
CC:	"Rafael J. Wysocki" <rjw@...k.pl>,
	"H. Peter Anvin" <hpa@...or.com>,
	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 04:32 AM, Stefano Stabellini wrote:
> On Thu, 31 Mar 2011, Yinghai Lu wrote:
>> Stefano, can you explain why it fixes the problem?
>>
>> or original patch uncover the bug?
>
> as I wrote in the other email, e5f15b45ddf3afa2bbbb10c7ea34fb32b6de0a0e
> removes cleanup_highmap_brk_end but this function was not only dealing
> with mappings but it was also setting mmu_cr4_features, therefore the
> setting of mmu_cr4_features was lost.
>
> I think the real bug is that mmu_cr4_features ended up in
> cleanup_highmap_brk_end by mistake.


originally mmu_cr4 is saved in init_memory_mapping.

and init_memory_mapping will update cr4.

so please use this version instead.


From: Stefano Stabellini <stefano.stabellini@...citrix.com>

[PATCH -v2] x86: Save cr4 to mmu_cr4_features at boot time

Save cr4 to mmu_cr4_features at boot time

Michael reported 2.6.38.2 hibernation is broken by one backported patch.
it cause a freeze when resuming from hibernation

| "x86: Cleanup highmap after brk is concluded"
| commit id e5f15b45ddf3afa2bbbb10c7ea34fb32b6de0a0e.

it turns out the mmu_cr4 save it lost somehow.

-v2: need to save mmu_cr4 after init_memory_mapping(), because it updates mmu_cr4
      and originally that storing action is after updating.  -- by Yinghai

Bisected-and-tested-by: Michael Leun <lkml20101129@...ton.leun.net>
Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
Signed-off-by: Yinghai Lu <yinghai@...nel.org>

---
  arch/x86/kernel/setup.c |    9 +++++++++
  1 file changed, 9 insertions(+)

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) {
--
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