linux-kernel - Re: [PATCH V2 1/6] perf/x86/intel: Add Grand Ridge and Sierra Forest

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Date:   Thu, 29 Jun 2023 15:39:39 -0700
From:   Tony Luck <tony.luck@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     "kan.liang@...ux.intel.com" <kan.liang@...ux.intel.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "acme@...nel.org" <acme@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "alexander.shishkin@...ux.intel.com" 
        <alexander.shishkin@...ux.intel.com>,
        "jolsa@...nel.org" <jolsa@...nel.org>,
        "namhyung@...nel.org" <namhyung@...nel.org>,
        "irogers@...gle.com" <irogers@...gle.com>,
        "Hunter, Adrian" <adrian.hunter@...el.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Eranian, Stephane" <eranian@...gle.com>,
        "alexey.v.bayduraev@...ux.intel.com" 
        <alexey.v.bayduraev@...ux.intel.com>,
        "Zhang, Tinghao" <tinghao.zhang@...el.com>
Subject: Re: [PATCH V2 1/6] perf/x86/intel: Add Grand Ridge and Sierra Forest

On Thu, Jun 08, 2023 at 04:20:22PM +0000, Luck, Tony wrote:
> > Then I'm hoping their take-away is that random gibberish names don't
> > help anybody. The whole Intel naming scheme is impenetrable crap.
> 
> > > +#define INTEL_FAM6_ATOM_CRESTMONT_X  0xAF /* Sierra Forest */
> > > +#define INTEL_FAM6_ATOM_CRESTMONT    0xB6 /* Grand Ridge */
> 
> This just adds another layer of confusion. Sure, these two models are based
> on the same core. But giving the illusion that they are somehow the same will
> lead to tears before bedtime:
> 
> 1) They each took a snapshot of that core design on different dates, so there
>    are logic differences.
> 2) Feature fuses will be different
> 3) Microcode will be different
> 4) BIOS will be different
> 5) "uncore" is different, so anything implemented outside of the core
>     will be different.

This thread stalled. But the internal conversation continued. There
seems a strong argument that enough things changed when Xeon-izing
the core to go into Sierra Forest that using Crestmont will cause
confusion in more places than it helps. There seem to be some internal
folks using an entirely different name for this core (which I won't
repeat here, but some of the usual external sites have mentions of
this other name).

Can we just keep:

#define INTEL_FAM6_SIERRAFOREST_X       0xAF

and move on to more interesting things?

-Tony