Re: [PATCH][2.5-AC] Forced enable/disable local APIC

Mikael Pettersson (mikpe@csd.uu.se)
Thu, 7 Nov 2002 17:14:29 +0100


Zwane Mwaikambo writes:
> +int enable_local_apic_flag __initdata = 0; /* 0=probe, 1=force, 2=disable e.g. DMI */
...
> + if (enable_local_apic_flag == 1)
> + goto force_apic;
>
> switch (boot_cpu_data.x86_vendor) {
> case X86_VENDOR_AMD:
> @@ -642,6 +661,7 @@
> goto no_apic;
> }
>
> +force_apic:
> if (!cpu_has_apic) {
> /*
> * Some BIOSes disable the local APIC in the

Of what use is the force case? If someone boots with "lapic" on a CPU
where the APIC feature bit is off, then the code will rdmsr/wrmsr on
APICBASE, even though we (the kernel) haven't verified that the CPU
actually has that MSR. This is doubleplusungood.

I have no problem with the disable option.

/Mikael
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