linux-kernel - Re: [PATCH] perf,x86,p6: Add userspace RDPMC quirk for P6

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Message-ID: <20140205195506.GN2936@laptop.programming.kicks-ass.net>
Date:	Wed, 5 Feb 2014 20:55:06 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vince Weaver <vince@...ter.net>
Cc:	junk@...af.co.uk, alan@...rguk.ukuu.org.uk,
	Ingo Molnar <mingo@...nel.org>,
	Stephane Eranian <eranian@...gle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf,x86,p6: Add userspace RDPMC quirk for P6

On Wed, Feb 05, 2014 at 02:37:29PM -0500, Vince Weaver wrote:
> On Wed, 5 Feb 2014, Vince Weaver wrote:
> 
> > Has someone actually hit this bug?  People used PAPI/perfctr on these 
> > machines for years, and it uses rdpmc by default so I would think it would 
> > show up if it were an issue.  I should check the perfctr code to see if it 
> > had some sort of check.
> 
> I can verify the perfctr code does have a case for PPRO errata 26, but it 
> only disables things on pentium pros with stepping less than 9.

The doc said 0xB1, right? Should we keep it at that? Its not like
there's a lot of PPro machines left out there, so better safe than
sorry.

> It also disables rdpmc on original Pentiums due to errata 74 but I don't 
> think we have to worry about that one.

We don't have a Family 5 driver, so no.
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