linux-kernel - Re: [PATCH 2/4] [APIC] Allow disabling of UP APIC/IO-APIC by default, with command line option to turn it on.

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Date:	Fri, 01 Dec 2006 15:56:36 -0500
From:	Ben Collins <ben.collins@...ntu.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Ben Collins <bcollins@...ntu.com>, linux-kernel@...r.kernel.org,
	torvalds@...l.org, Andrew Morton <akpm@...l.org>
Subject: Re: [PATCH 2/4] [APIC] Allow disabling of UP APIC/IO-APIC by
	default, with command line option to turn it on.

On Fri, 2006-12-01 at 09:39 +0100, Ingo Molnar wrote:
> * Ben Collins <bcollins@...ntu.com> wrote:

> that should be "ioapic", not "apic". The CPU has a piece of silicon 
> called the "local APIC" - enabled via the 'lapic' option, and disabled 
> via noapic. What the option above wants to enable is the IO-APIC in the 
> chipset (a different piece of silicon) and the interrupt routing 
> capabilities attached to it. That piece is what is causing the installer 
> problems.

I know the difference between APIC and IO-APIC :)

Thing is, the function right above the one I added was this:

static int __init parse_noapic(char *arg)
{
        /* disable IO-APIC */
        disable_ioapic_setup();
        return 0;
}
early_param("noapic", parse_noapic);

So while "ioapic" might make more sense, it's doesn't match the opposing
command line option of "noapic".

I could include this in the diff:

+/* "noapic" is for backward compatibility */
 early_param("noapic", parse_noapic);
+early_param("noioapic", parse_noapic);

And then add the "ioapic" option.
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