Messages in this thread | | | Date | Fri, 01 Apr 2011 14:42:30 -0700 | From | "H. Peter Anvin" <> | Subject | Re: 2.6.38.2 breaks suspend to disk |
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On 04/01/2011 02:37 PM, Yinghai Lu wrote: >> >> Err, yes, that's what I meant. >> >> Now, why the heck did you introduce a bunch of CONFIG_HIBERNATION #ifdefs? > > mmu_cr4_features: have two usages: > 1. for 32bit to control cr4 access in head_32.S > 2. for hibernation resume. > > include/asm/processor.h:extern unsigned long mmu_cr4_features; > include/asm/processor.h: mmu_cr4_features |= mask; > include/asm/processor.h: mmu_cr4_features &= ~mask; > kernel/head_32.S:#define cr4_bits pa(mmu_cr4_features) > kernel/setup.c: * mmu_cr4_features two purpose: > kernel/setup.c:unsigned long mmu_cr4_features; > kernel/setup.c:unsigned long mmu_cr4_features = X86_CR4_PAE; > kernel/setup.c: mmu_cr4_features = read_cr4(); > power/hibernate_asm_32.S: movl mmu_cr4_features, %ecx > power/hibernate_asm_32.S: movl mmu_cr4_features, %ecx > power/hibernate_asm_64.S: movq mmu_cr4_features(%rip), %rax > power/hibernate_asm_64.S: movq mmu_cr4_features(%rip), %rax > > So we don't need to read back cr4 and save it if CONFIG_HIBERNATION is > not defined. >
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?
-hpa
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