Date: Wed, 30 Nov 2005 10:07:04 +1100
From: David Gibson <david@gibson.dropbear.id.au>
To: Andi Kleen <ak@suse.de>
Cc: Nicholas Miell <nmiell@comcast.net>, Stephane Eranian <eranian@hpl.hp.com>,
       Ray Bryant <raybry@mpdtxmail.amd.com>, discuss@x86-64.org,
       linux-kernel@vger.kernel.org, perfctr-devel@lists.sourceforge.net
Subject: Re: [Perfctr-devel] Re: Enabling RDPMC in user space by default
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	Andi Kleen <ak@suse.de>, Nicholas Miell <nmiell@comcast.net>,
	Stephane Eranian <eranian@hpl.hp.com>,
	Ray Bryant <raybry@mpdtxmail.amd.com>, discuss@x86-64.org,
	linux-kernel@vger.kernel.org, perfctr-devel@lists.sourceforge.net
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On Tue, Nov 29, 2005 at 11:43:47PM +0100, Andi Kleen wrote:
> > Well, RDPMC isn't defined at all. You're assuming that future processor
> > revisions will have the same or substantially similar PerfCtrs as
> > current processors, and nothing guarantees that at all.
> 
> Point, but i guess it is reasonable to assume that future x85 CPUs
> will have cycle counter perfctrs.  I cannot imagine anybody dropping
> such a basic facility.

It need not necessarily remain configurable to be in PMC 0 however.
Nor do the the PMC MSRs have to remain fixed..

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
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