linux-hardening - Re: [PATCH v3 08/10] perf/x86/rapl: Modify the generic variable names to *

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Message-ID: <477c33a2949793d2a8692c925179bc4f1feb7942.camel@intel.com>
Date: Tue, 2 Jul 2024 02:25:27 +0000
From: "Zhang, Rui" <rui.zhang@...el.com>
To: "peterz@...radead.org" <peterz@...radead.org>, "Dhananjay.Ugwekar@....com"
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Subject: Re: [PATCH v3 08/10] perf/x86/rapl: Modify the generic variable names
 to *_pkg*

On Mon, 2024-07-01 at 15:08 +0200, Peter Zijlstra wrote:
> On Mon, Jun 24, 2024 at 05:59:05AM +0000, Dhananjay Ugwekar wrote:
> > Prep for addition of power_per_core PMU to handle core scope energy
> > consumption for AMD CPUs.
> > 
> > Replace the generic names with *_pkg*, to differentiate between the
> > scopes of the two different PMUs and their variables.
> 
> But then remember patch 2 and recall that intel seems to have
> everything
> at die level, not pkg.
> 
> Does this proposed naming make sense? How?

For Intel products, we have
1. Casecadelake-AP which has multi-die per package and has per-die RAPL
MSRs
2. all other platforms which has single-die per package, so its RAPL
MSRs can be considered as either package-scope or die-scope
This applies to Thermal MSRs as well.

so for these MSRs, we can treat them as
1. always die-scope for all existing platforms
or
2. package-scope with the exception of Casecadelake-ap
And current kernel code follows rule 1.

I propose we switch to rule 2 for these code because rule 1 can be
broke on future multi-die systems (This is already true for Thermal
MSRs).

In this sense, I think it is okay to call it pkg level rapl for both
Intel and AMD.

thanks,
rui