linux-kernel - Re: [patch 3/6] x86: use cpuinfo to check for interrupt pending message msr

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Date:	Fri, 13 Jun 2008 16:28:43 +0200
From:	Andreas Herrmann <andreas.herrmann3@....com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Arjan van de Veen <arjan@...radead.org>
Subject: Re: [patch 3/6] x86: use cpuinfo to check for interrupt pending
	message msr

On Fri, Jun 13, 2008 at 02:38:30PM +0200, Thomas Gleixner wrote:
> On Fri, 13 Jun 2008, Andreas Herrmann wrote:
> > > +	/* Family 0x0f models < rev F do not have this MSR */
> > > +	if (c->x86 == 0x0f && c->x86_model < 0x40)
> > > +		return 0;
> > 
> > Just some minor nitpicking.
> > Older AMD family 0xf CPUs have this Interrupt Pending Message
> > Register. But they do not support C1E and thus bits 27 and 28 of this
> > MSR are reserved.
> 
> So the check can be simplified to always check the MSR for all 
> family >= 0x0f CPUs ?

First of all I thought of changing the comment.

But now that you ask:
Documentation for older K8 CPUs says that reserved bits in that MSR
are "Read as Zero". But otherwise it also says "Software must not
depend on the state of a reserved field ..."

Maybe I am a little paranoid but I would keep the model check.


Andreas


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