Messages in this thread | | | From | Johannes Weiner <> | Subject | Re: [PATCH] Option to disable AMD C1E (allows dynticks to work) | Date | Thu, 13 Dec 2007 23:58:50 +0100 |
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Hi,
Eduard-Gabriel Munteanu <eduard.munteanu@linux360.ro> writes:
> diff --git a/arch/x86/kernel/setup_64.c b/arch/x86/kernel/setup_64.c > index 30d94d1..15556a0 100644 > --- a/arch/x86/kernel/setup_64.c > +++ b/arch/x86/kernel/setup_64.c > @@ -583,6 +583,17 @@ static void __init amd_detect_cmp(struct cpuinfo_x86 *c) > #endif > } > > +#ifdef CONFIG_X86_AMD_C1E_WORKAROUND > +static int __cpuinit disable_amd_c1e = 1; > + > +static int __cpuinit force_amd_c1e(char *str) { > + disable_amd_c1e = 0; > + return 1; > +} > + > +__setup("force_amd_c1e", force_amd_c1e); > +#endif /* CONFIG_X86_AMD_C1E_WORKAROUND */ > + > #define ENABLE_C1E_MASK 0x18000000 > #define CPUID_PROCESSOR_SIGNATURE 1 > #define CPUID_XFAM 0x0ff00000 > @@ -597,6 +608,7 @@ static __cpuinit int amd_apic_timer_broken(void) > { > u32 lo, hi; > u32 eax = cpuid_eax(CPUID_PROCESSOR_SIGNATURE); > + > switch (eax & CPUID_XFAM) { > case CPUID_XFAM_K8: > if ((eax & CPUID_XMOD) < CPUID_XMOD_REV_F) > @@ -604,8 +616,19 @@ static __cpuinit int amd_apic_timer_broken(void) > case CPUID_XFAM_10H: > case CPUID_XFAM_11H: > rdmsr(MSR_K8_ENABLE_C1E, lo, hi); > - if (lo & ENABLE_C1E_MASK) > - return 1; > +#ifdef CONFIG_X86_AMD_C1E_WORKAROUND > + if ((lo & ENABLE_C1E_MASK) && disable_amd_c1e) { > + printk(KERN_INFO "Disabling AMD C1E on CPU %d\n", > + smp_processor_id()); > + /* > + * See AMD's "BIOS and Kernel Developer's Guide for AMD > + * NPT Family 0Fh Processors", publication #32559, > + * for details. > + */ > + wrmsr(MSR_K8_ENABLE_C1E, lo & ~ENABLE_C1E_MASK, hi); > + } else > +#endif /* CONFIG_X86_AMD_C1E_WORKAROUND */ > + if (lo & ENABLE_C1E_MASK) return 1;
I would find this way more readable:
if (lo & ENABLE_C1E_MASK) { #ifdef CONFIG_X86_AMD_C1E_WORKAROUND if (disable_amd_c1e) { ... #else return 1; #endif }
Why does it require to be enabled by compile-time AND run-time? Is that something you might want to decide on every boot? Could we make it settable at boot-time xor at compile-time?
Hannes
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