Messages in this thread | | | Subject | Re: [PATCH] Fix i486 suspend to disk CR4 oops | From | Andi Kleen <> | Date | Mon, 18 Aug 2008 08:04:51 +0200 |
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"H. Peter Anvin" <hpa@zytor.com> writes:
> Maciej W. Rozycki wrote: >> On Sun, 17 Aug 2008, David Fries wrote: >> >>> arch/x86/power/cpu_32.c __save_processor_state calls read_cr4() >>> only a i486 CPU doesn't have the CR4 register. Trying to read it >>> produces an invalid opcode oops during suspend to disk. >> [...] >>> diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c >>> index 81e5ab6..bd0f2a3 100644 >>> --- a/arch/x86/kernel/acpi/sleep.c >>> +++ b/arch/x86/kernel/acpi/sleep.c >>> @@ -86,7 +86,9 @@ int acpi_save_state_mem(void) >>> #endif /* !CONFIG_64BIT */ >>> header->pmode_cr0 = read_cr0(); >>> - header->pmode_cr4 = read_cr4(); >>> + /* cr4 was introduced in the Pentium CPU */ >>> + if (boot_cpu_data.x86 >= 5) >>> + header->pmode_cr4 = read_cr4(); >>> header->realmode_flags = acpi_realmode_flags; >>> header->real_magic = 0x12345678; >>> >> NACK. Later i486 chips do have CR4 -- for PSE, VME, etc. (the set >> of >> features varies across the line). Use a fixup as elsewhere or something. >> > > The other alternative is to probe for the CPUID instruction (via > EFLAGS.ID) -- CR4 is present if and only if CPUID exists.
Can be already checked for with boot_cpu_data.extended_cpuid_level.
-Andi
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