Re: 2.6.38.2 breaks suspend to disk

[Yinghai Lu]

On Fri, Apr 1, 2011 at 1:21 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> On 04/01/2011 12:54 PM, Yinghai Lu wrote:
>>
>> ok, please check if you are happy with this one.
>>
>
> The best would simply be:
>
>        mmu_cr4_features = read_cr4_safe();
>
> If this has to run before we can handle exceptions, one can verify the
> existence by testing for the CPUID instruction (a CPU has CR4 if and
> only if it has CPUID):
>
>        if (boot_cpu_data.cpuid_level >= 0)
>                mmu_cr4_features = read_cr4_safe();
>
> ... since we set cpuid_level to -1 if there is no CPUID instruction.

in that case could use read_cr4 directly.

please check attached -v4

Thanks
From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

[PATCH -v4] 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

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 |    4 ++++
 arch/x86/kernel/setup.c          |   11 ++++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

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
@@ -212,7 +212,11 @@ struct cpuinfo_x86 boot_cpu_data __read_
 EXPORT_SYMBOL(boot_cpu_data);
 #endif
 
-
+/*
+ * mmu_cr4_features two purpose:
+ *  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
@@ -892,6 +896,11 @@ void __init setup_arch(char **cmdline_p)
 
 	high_memory = (void *)__va(max_pfn * PAGE_SIZE - 1) + 1;
 #endif
+#ifdef CONFIG_HIBERNATION
+	/* a CPU has CR4 iff it has CPUID --- hpa */
+	if (boot_cpu_data.cpuid_level >= 0)
+		mmu_cr4_features = read_cr4();
+#endif
 
 	/*
 	 * Find and reserve possible boot-time SMP configuration:
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 +601,9 @@ static inline void set_in_cr4(unsigned l
 {
 	unsigned long cr4;
 
+#ifdef CONFIG_HIBERNATION
 	mmu_cr4_features |= mask;
+#endif
 	cr4 = read_cr4();
 	cr4 |= mask;
 	write_cr4(cr4);
@@ -611,7 +613,9 @@ static inline void clear_in_cr4(unsigned
 {
 	unsigned long cr4;
 
+#ifdef CONFIG_HIBERNATION
 	mmu_cr4_features &= ~mask;
+#endif
 	cr4 = read_cr4();
 	cr4 &= ~mask;
 	write_cr4(cr4);