linux-kernel - Re: [PATCH] i386-pda: Initialize the PDA early, before any C code runs.

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Message-ID: <20060912055735.GB24298@elte.hu>
Date:	Tue, 12 Sep 2006 07:57:35 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Andrew Morton <akpm@...l.org>, Andi Kleen <ak@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] i386-pda: Initialize the PDA early, before any C code runs.


* Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> Jeremy Fitzhardinge wrote:
> >Not sure, but I think this replicates the behaviour of the original 
> >code (ie, INIT_THREAD_INFO initializes cpu to 0, so smp_processor_id 
> >will return 0).  Hm, Voyager will probably need a little patch to 
> >update the the PDA cpu_number properly in smp_setup_processor_id().
> 
> Something like this, perhaps:
> 
> Subject: set the boot CPU number in the boot_pda
> 
> Signed-off-by: Jeremy Fitzhardinge <jeremy@...source.com>

> +++ b/arch/i386/mach-voyager/voyager_smp.c	Mon Sep 11 16:34:09 2006 

> smp_setup_processor_id(void)
> {
> 	current_thread_info()->cpu = hard_smp_processor_id();
> -}
> +	write_pda(cpu_number, hard_smp_processor_id());
> +}

yeah. On all other x86 SMP platforms we use the logical APIC ID 0 for 
the boot CPU. (the physical ID might be different, but that doesnt 
matter)

NOTE: you'll also need to patch smp_voyager.c:find_smp_config(), where 
it sets current_thread_info()->cpu to boot_cpu_id.

	Ingo
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