linux-kernel - Re: [PATCH 4/9] x86: Initialize 32bit logical apicid mapping early during boot

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Date:	Thu, 11 Nov 2010 20:54:51 -0500
From:	Brian Gerst <brgerst@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de,
	hpa@...or.com, x86@...nel.org, eric.dumazet@...il.com,
	yinghai@...nel.org
Subject: Re: [PATCH 4/9] x86: Initialize 32bit logical apicid mapping early
 during boot

On Thu, Nov 11, 2010 at 6:02 AM, Tejun Heo <tj@...nel.org> wrote:
> On x86_32, non-standard logical apicid mapping can be used by
> different NUMA setups and the mapping is queried while bringing up
> each CPU using apic->cpu_to_logical_apicid() to build
> cpu_2_logical_apicid[] array.  The logical apicid is then used to
> deliver IPIs and determine NUMA configuration.
>
> Unfortunately, initializing at SMP bring up is too late for percpu
> setup making static percpu variables setup w/o considering NUMA.  This
> also is different from how x86_64 is configured making the code
> difficult to follow and maintain.
>
> This patch updates logical apicid mapping handling such that,
>
> * early_percpu variable x86_cpu_to_logical_apicid replaces
>  cpu_2_logical_apicid[].

You are missing code in setup_percpu.c to copy the values from the
early array to the percpu variable.  This isn't handled automatically.

Also make sure that any direct use of the percpu variable (ie. not via
early_per_cpu()) can happen only after percpu setup.

--
Brian Gerst
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