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

From: Maciej W. Rozycki (macro@ds2.pg.gda.pl)
Date: Thu Nov 07 2002 - 11:25:45 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.

 The assumption is a user knows better what he wants to achieve. But I'm
not sure we really need it here. A DMI override with the APICBASE
availability test in place should suffice -- I'd remove the "goto".

-- 
+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+--------------------------------------------------------------+
+        e-mail: macro@ds2.pg.gda.pl, PGP key available        +

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