Re: [PATCH] fix SMP kernel on SMP MoBo with APIC-less CPU

From: Christoph Hellwig (hch@caldera.de)
Date: Tue Aug 08 2000 - 11:30:19 EST

On Tue, Aug 08, 2000 at 09:15:50AM -0700, Linus Torvalds wrote:
>
>
> On Tue, 8 Aug 2000, Christoph Hellwig wrote:
> >
> > The Subjecy says it all:
> > This patch fixes booting of a SMP-compiled i386 kernel on a SMP-capable
> > motherboard with (one) non SMP-capable (= APIC-less) CPU.
> > Example: AMD K6 in a dual i430TX board.
>
> I understand why you'd want to do this,

One of my workmates here has such a combination.
He tried to install the current Linux Technologie Preview
(our Beta based on Linux 2.4) which has only SMP-Support but
it didn't work ....

> but I suspect this will also break
> _real_ SMP setups that have non-local APICs (ie old intel CPU's).

Ok, here's a new version, that checks for a generation 5 and higher
processor.

        Christoph 

-- 
Always remember that you are unique.  Just like everyone else.

--- linux/arch/i386/kernel/setup.c~	Wed Jul 26 23:03:18 2000
+++ linux/arch/i386/kernel/setup.c	Tue Aug  8 18:26:29 2000
@@ -758,7 +758,9 @@
 	/*
 	 * get boot-time SMP configuration:
 	 */
-	if (smp_found_config)
+	/* if up-to date cpu, try only if the cpu has a local apic */
+	if (smp_found_config && (boot_cpu_data.x86 >= 5
+			&& (boot_cpu_data.x86_capability & X86_FEATURE_APIC)))
 		get_smp_config();
 #endif
 #ifdef CONFIG_X86_LOCAL_APIC

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