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SubjectRe: [RFC -tip] x86,apic -- reduce disable_apic usage
[H. Peter Anvin - Sun, Jul 05, 2009 at 10:30:11AM -0700]
| Maciej W. Rozycki wrote:
| >
| > How do you set cpu_has_apic for systems with discrete local APICs? The
| > CPUID flag is not set in this case.
| >
|
| Well, should it be? We do set flags when they're appropriate to us, and
| if the semantics are such as that is inappropriate we can set a custom bit.
|
| -hpa
|

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.

-- Cyrill


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