Re: [PATCH] i386 kexec: Allow the kexec on panic support to compile on voyager.

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

Horms <horms@verge.net.au> writes:

> On Mon, 10 Jul 2006 16:37:49 -0600, Eric W. Biederman wrote:
>> 
>> This patch removes the foolish assumption that SMP implied local
>> apics.  That assumption is not-true on the Voyager subarch.  This
>> makes that dependency explicit, and allows the code to build.
>
> Doesn't only a small portion of the code in question rely
> on CONFIG_X86_LOCAL_APIC? Is just a workaround until proper
> voager support materialises?

Essentially, but it is correct for the code to stay this way.

>> What gets disabled is just an optimization to get better crash
>> dumps so the support should work if there is a kernel that will
>> initialization on the voyager subarch under those harsh conditions.
>
> By that do you mean, a crash kernel that is able to boot even
> though the non-crashing CPUs have not been shutdown?

I simply mean a crash kernel that is able to boot.

>> Hopefully we can figure out how to initialize apics in init_IRQ
>> and remove the need to disable io_apics and this dependency.
>
> That does sound nice. Do you have any ideas on how that could be 
> made to happen?

My patch for that got reverted because it wouldn't boot on Linus's
SMP laptop.  It appeared to be some weird ACPI problem.  I didn't
receive any bug reports otherwise.

So I suspect the steps are:
1) Unify SMP and non-SMP apic initialization so it is the exact same
   code.
2) Move the unified code up in the boot sequence into init_IRQs.

It is something that needs to be done very delicately.

Eric