Re: 2.6.38.2 breaks suspend to disk

[Yinghai Lu]

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.

Thanks

Yinghai

From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

[PATCH -v5] 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
-v4: use cpuid_level to check if we can read cr4 according to HPA
     don't touch mmu_cr4_features if CONFIG_HIBERNATION is defined from Yinghai
-v5: reduce the using of CONFIG_HIBERNATION

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/include/asm/processor.h  |    2 --
 arch/x86/include/asm/suspend_32.h |    2 +-
 arch/x86/include/asm/suspend_64.h |    5 +----
 arch/x86/kernel/setup.c           |   16 +++++++++++++++-
 4 files changed, 17 insertions(+), 8 deletions(-)

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
@@ -212,12 +212,26 @@ struct cpuinfo_x86 boot_cpu_data __read_
 EXPORT_SYMBOL(boot_cpu_data);
 #endif
 
-
+/*
+ * mmu_cr4_features has two purposes:
+ *  a. head_32.S will access cr4 according if X86_CR4_PAE is set in it.
+ *  b. store read back cr4 for hibernation
+ */
 #if !defined(CONFIG_X86_PAE) || defined(CONFIG_X86_64)
 unsigned long mmu_cr4_features;
 #else
 unsigned long mmu_cr4_features = X86_CR4_PAE;
 #endif
+#ifdef CONFIG_HIBERNATION
+int arch_prepare_suspend(void)
+{
+	/* a CPU has CR4 iff it has CPUID --- hpa */
+	if (boot_cpu_data.cpuid_level >= 0)
+		mmu_cr4_features = read_cr4();
+
+	return 0;
+}
+#endif
 
 /* Boot loader ID and version as integers, for the benefit of proc_dointvec */
 int bootloader_type, bootloader_version;
Index: linux-2.6/arch/x86/include/asm/processor.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/processor.h
+++ linux-2.6/arch/x86/include/asm/processor.h
@@ -601,7 +601,6 @@ static inline void set_in_cr4(unsigned l
 {
 	unsigned long cr4;
 
-	mmu_cr4_features |= mask;
 	cr4 = read_cr4();
 	cr4 |= mask;
 	write_cr4(cr4);
@@ -611,7 +610,6 @@ static inline void clear_in_cr4(unsigned
 {
 	unsigned long cr4;
 
-	mmu_cr4_features &= ~mask;
 	cr4 = read_cr4();
 	cr4 &= ~mask;
 	write_cr4(cr4);
Index: linux-2.6/arch/x86/include/asm/suspend_32.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/suspend_32.h
+++ linux-2.6/arch/x86/include/asm/suspend_32.h
@@ -9,7 +9,7 @@
 #include <asm/desc.h>
 #include <asm/i387.h>
 
-static inline int arch_prepare_suspend(void) { return 0; }
+int arch_prepare_suspend(void);
 
 /* image of the saved processor state */
 struct saved_context {
Index: linux-2.6/arch/x86/include/asm/suspend_64.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/suspend_64.h
+++ linux-2.6/arch/x86/include/asm/suspend_64.h
@@ -9,10 +9,7 @@
 #include <asm/desc.h>
 #include <asm/i387.h>
 
-static inline int arch_prepare_suspend(void)
-{
-	return 0;
-}
+int arch_prepare_suspend(void);
 
 /*
  * Image of the saved processor state, used by the low level ACPI suspend to
--
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