On 07/10/2013 01:52 PM, Christian Sünkenberg wrote: > Hello, > > On 05/01/2013 07:33 PM, H. Peter Anvin wrote: >> On 05/01/2013 10:01 AM, Jonas Heinrich wrote: >>> Hello, I tried the newest kernel, 3.9 today but the bug is still >>> present. Applying the attached patch solves the bug for me. >>> >>> Best regards, Jonas Heinrich >> >> Okay... WTF is going on here? Does pmode_behavior just not get set up >> correctly? Since it seems you can get it to wake up with your patch, >> perhaps we can get read out the value of pmode_behavior and print it... > > indeed, arch/x86/kernel/acpi/sleep.c tries an rdmsr_safe(MSR_EFER, ...) > and sets WAKEUP_BEHAVIOR_RESTORE_EFER bit on success, however, > on 90 nm Pentium M (Family 6, Model 13), reading an invalid MSR > is not guaranteed to trap, see Erratum X4 in "Intel® Pentium® M > Processor on 90 nm Process with 2-MB L2 Cache and Intel® Processor A100 > and A110 on 90 nm process with 512-KB L2 Cache Specification Update". > On Jonas' T43, which has an affected Pentium M without EFER, > rdmsr_safe(MSR_EFER, ...) succeeds and WAKEUP_BEHAVIOR_RESTORE_EFER > gets set, while on resume the corresponding wrmsr traps and thus resume > fails. > > The pre-3.7 code snippet incidentally catched this by not restoring > EFER when it would be restored to all 0s. >
That does seem like a reasonable explanation. Does this patch fix the problem? (Comment blatantly ripped off from your email message.) -hpa
diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c index b44577b..927c5ce 100644 --- a/arch/x86/kernel/acpi/sleep.c +++ b/arch/x86/kernel/acpi/sleep.c @@ -48,9 +48,20 @@ int acpi_suspend_lowlevel(void) #ifndef CONFIG_64BIT native_store_gdt((struct desc_ptr *)&header->pmode_gdt); + /* + * We have to check that we can write back the value, and not + * just read it. At least on 90 nm Pentium M (Family 6, Model + * 13), reading an invalid MSR is not guaranteed to trap, see + * Erratum X4 in "Intel Pentium M Processor on 90 nm Process + * with 2-MB L2 Cache and Intel® Processor A100 and A110 on 90 + * nm process with 512-KB L2 Cache Specification Update". + */ if (!rdmsr_safe(MSR_EFER, &header->pmode_efer_low, - &header->pmode_efer_high)) + &header->pmode_efer_high) && + !wrmsr_safe(MSR_EFER, + header->pmode_efer_low, + header->pmode_efer_high)) header->pmode_behavior |= (1 << WAKEUP_BEHAVIOR_RESTORE_EFER); #endif /* !CONFIG_64BIT */