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

From: Zwane Mwaikambo (zwane@holomorphy.com)
Date: Thu Nov 07 2002 - 11:41:23 EST

On Thu, 7 Nov 2002, Mikael Pettersson wrote:

> 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.

We still honour the APIC feature bit, its just that we bypass the cpuid
checks. Looks sane no?

        Zwane 

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function.linuxpower.ca

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