linux-kernel - Re: [PATCH 2/3] x86/topology: Fix AMD core count

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Message-ID: <20160320123225.GN6344@twins.programming.kicks-ass.net>
Date:	Sun, 20 Mar 2016 13:32:25 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>, aherrmann@...e.com,
	jencce.kernel@...il.com, Rui Huang <ray.huang@....com>
Subject: Re: [PATCH 2/3] x86/topology: Fix AMD core count

On Sun, Mar 20, 2016 at 12:04:55PM +0100, Borislav Petkov wrote:
> On Sun, Mar 20, 2016 at 11:39:46AM +0100, Peter Zijlstra wrote:
> > So the AMD NB stuff in events/amd/core.c is only for Fam10, Fam15 got
> > its own uncore driver. (Fam10 had the uncore events through the same
> > counters as the core PMU with with 'fun' constraints).
> > 
> > And since Fam10 isn't affected by this change in x86_max_cores, this
> > _should_ work out, IF that NB code knows to switch off properly when not
> > required.
> 
> But but, amd_core_pmu_init() is called on F15h too. It only gets the
> different F15h event constraints and MSRs...

Yes, but IIRC the F15h driver doesn't use the NB constraints, as they
moved all the NB events to their own set of MSRs, which has
events/amd/uncore.c.

So all the NB cruft in the core pmu is only relevant to F10h.

So F15h also calling and allocating NB cruft in the core PMU driver is
entirely pointless.