Re: 2.6.38.2 breaks suspend to disk

[Yinghai Lu]

On 04/01/2011 12:36 PM, H. Peter Anvin wrote:
> On 04/01/2011 12:32 PM, Yinghai Lu wrote:
> > So for 32 bit, PAE support is not compiled in for old 486 cpus.
> > mmu_cr4_feautres will be used to make sure head_32.S will not access cr4.
> >
> > that could be the reason why 32 bit does not do read back at beginning.
>
> Yes, but that doesn't explain why we shouldn't set new bits like NX and
> PSE in this register.

ok, please check if you are happy with this one.

From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

[PATCH -v3] 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.

-v3: read back cr4 for 32bit too according to HPA

Bisected-and-tested-by: Michael Leun <lkml20101129@xxxxxxxxxxxxxxx>
Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>

---
 arch/x86/kernel/setup.c |   12 ++++++++++++
 1 file changed, 12 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
@@ -219,6 +219,17 @@ unsigned long mmu_cr4_features;
 unsigned long mmu_cr4_features = X86_CR4_PAE;
 #endif
 
+#if defined(CONFIG_X86_PAE) || defined(CONFIG_X86_64)
+static void __init read_back_mmu_cr4(void)
+{
+	mmu_cr4_features = read_cr4();
+}
+#else
+static void __init read_back_mmu_cr4(void)
+{
+}
+#endif
+
 /* Boot loader ID and version as integers, for the benefit of proc_dointvec */
 int bootloader_type, bootloader_version;
 
@@ -892,6 +903,7 @@ void __init setup_arch(char **cmdline_p)
 
 	high_memory = (void *)__va(max_pfn * PAGE_SIZE - 1) + 1;
 #endif
+	read_back_mmu_cr4();
 
 	/*
 	 * Find and reserve possible boot-time SMP configuration:
--
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