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Date: Thu, 29 Mar 2007 14:16:54 -0700 (PDT)
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Andi Kleen <ak@suse.de>
cc: Mark Langsdorf <mark.langsdorf@amd.com>, Len Brown <lenb@kernel.org>,
       "Morrow, William" <William.Morrow@amd.com>,
       "Crouse, Jordan" <jordan.crouse@ldcmail.amd.com>,
       Thomas Gleixner <tglx@linutronix.de>, Pavel Machek <pavel@ucw.cz>,
       Ingo Molnar <mingo@elte.hu>,
       "Eric W. Biederman" <ebiederm@xmission.com>,
       Nick Piggin <nickpiggin@yahoo.com.au>, Mingming Cao <cmm@us.ibm.com>,
       Adrian Bunk <bunk@stusta.de>, Andrew Morton <akpm@linux-foundation.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
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       Oliver Pinter <oliver.pntr@gmail.com>,
       Sid Boyce <g3vbv@blueyonder.co.uk>, Nick Piggin <npiggin@suse.de>,
       Jens Axboe <jens.axboe@oracle.com>, Thomas Renninger <trenn@suse.de>
Subject: Re: [PATCH] i386: add command line option "local_apic_timer_c2_ok"
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On Thu, 29 Mar 2007, Andi Kleen wrote:
> 
> Here's a patch. I don't have a system with C1E, so i only tested that
> the apic timer still works on a older AMD box.

I think this looks better than what we have now, but it would look even 
better if the core CPUID stuff was in arch/i386/kernel/cpu/amd.c, and we 
simply had X86_FEATURE_BROKEN_C1_LAPIC etc..

And then the apic.c code would just check

	if (boot_cpu_has(X86_FEATURE_BROKEN_C1_LAPIC))
		return -1;

or similar.

Doing the same for C2 and C3 gives us a clean way to have all these 
per-vendor things in their relevant places, rather than having various 
vendor-specific checks sprinkled in random places..

That's *especially* true for something like this that can hit both on 
x86-64 and i386, where the cpuid logic is shared, but the APIC logic is 
*not* shared. If I read your patch correctly, this only fixes it on 32-bit 
platforms, and I don't think the problem is in any way 32-bit specific, is 
it?

		Linus