Re: [RFC -tip] x86,apic -- reduce disable_apic usage

["H. Peter Anvin" <hpa@zytor.com>]

Cyrill Gorcunov wrote:
> 
> Peter, Maciej but how kernel behaved on older cpu long time ago?
> 
> I mean -- should user pass "lapic" cmdline option too be
> able to use apic functionality? (i'm asking since I just
> don't know how it had been working before). Current
> code (if only I'm not _missing_ something) relies on cpu_has_apic
> bit. And even if MP table has been parsed and APIC base found,
> cpu_has_apic could be not set so detect_init_APIC will fail
> if no "lapic" option passed (in case of old cpu without this cpuid
> bit produced) as we eventually stay with pic mode.
> 

Well, systems with discrete APICs were few and far between.  I'm not
sure if there are any such systems still in meaningful existence (kind
of like Voyager.)  That makes it a bit hard to test things, and
certainly means we shouldn't bend over backwards in doing *anything*
that could possibly break other machines.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.