Re: [Fastboot] Re: kdump on non-boot cpu

[ebiederm@xmission.com (Eric W. Biederman)]

Itsuro Oda <oda@valinux.co.jp> writes:

> > So I believe the fix needs to be to enable apics before we calibrate
> > the delay timer.  I'm not certain off the top of my head what that
> > patch will look like but it should not be fundamentally hard.  
> > With that code in place we also don't need to do any APIC shutdown
> > as the kernel knows enough to completely setup the apics.
> 
> I see. Thank you for your explanation.

I have done a bit more digging.

For some reason, likely historical we don't initialize the
IO_APIC in init_IRQ().  Instead we wait until smp_prepare_cpus() or
smp_init().  Both functions are called much later in the init process
than calibrate_delay().

Given the separation that has happened between apics and SMP it should
be possible to initialize the local apic and the IO_APIC of the boot
cpu much earlier in the game.  It looks like it may take some heavy
lifting though.

Eric