Re: [PATCH] x86,apic: Checking kernel option before detect_init_APIC()

[Cyrill Gorcunov <gorcunov@gmail.com>]

[Rakib Mullick - Thu, Apr 09, 2009 at 11:08:43AM +0600]
| On Wed, Apr 8, 2009 at 8:50 PM, Ingo Molnar <mingo@elte.hu> wrote:
| >
| > * Rakib Mullick <rakib.mullick@gmail.com> wrote:
| >
| > Hm, are you sure this is a cleanup only? (i.e. no side-effects)
| My quick review over code, i don't think there's any.Unless I'm not
| missing anything. Kernel option has been passed when before kernel
| starts, so I think it's safe.

Hi Rakib,

yes, disable_apic early parameter handled earlier then
init_apic_mappings is being called but we could reach
disable_apic=1 with not only as kernel option but as
result of acpi_mps_check for example (which
is called earlier then init_apic_mappings though).
So this snippet is safe I believe.

| >
| > Also, even if it's a pure cleanup, wouldnt it be even cleaner to
| > propagate this check into detect_init_APIC() - and thus get rid of
| > the open-coded disable_apic check altogether?

In point! We do same fasion check in APIC_init_uniprocessor

| Yes, could be. How we'll understand that whether apic has been
| disabled from kernel option or not (if we requires later on)?

AFAIS, as only we set disable_apic=1 from kernel option (or other
ways) we clear X86_FEATURE_APIC likewise. So I don't see easy way
to distinguish the reason why apic is disabled. But to be precise
APIC_init_uniprocessor print us some info.

So I'm for Ingo's idea!

| 
| Rakib
| >
| >        Ingo
| >
| 
        Cyrill