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

[Mikael Pettersson]

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