linux-kernel - Re: [patch] x86 CPU detection for RDC

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Message-ID: <20090817213118.GA24747@one.firstfloor.org>
Date:	Mon, 17 Aug 2009 23:31:18 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	Mark Kelly <mark@...feros.com>, linux-kernel@...r.kernel.org,
	Florian Fainelli <florian@...nwrt.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch] x86 CPU detection for RDC

> It isn't a matter of if compilation works, it is a matter of if we

I was actually wrong -- someone moved the functions out of line.
So CONFIG_PCI is needed after all.

> should even try to probe PCI if the user has explicitly disabled
> CONFIG_PCI.  arch/x86/kernel/cpu/cyrix.c disables its PCI probing if
> CONFIG_PCI is off, even though it also uses <asm/pci-direct.h>.

Better would be if he used early_pci_allowed() then this could
be set at runtime.

> Given that the benefit of this CPU detection patch is extremely small
> (all it does it get better information in /proc/cpuinfo) and that blind
> probing can have disastrous consequences, I would say it should not.

I thought it was to prevent oopses for zero cpu according
to the reporter?

But these oopses should be probably separately fixed anyways.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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