linux-kernel - Re: [PATCH 1/2 RESEND3] perf/x86/amd/uncore: Do not set ThreadMask and SliceMask for non-L3 PMCs

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Date:   Mon, 1 Jul 2019 10:21:48 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Phillips, Kim" <kim.phillips@....com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Martin Liska <mliska@...e.cz>,
        "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@....com>,
        "Natarajan, Janakarajan" <Janakarajan.Natarajan@....com>,
        "Hook, Gary" <Gary.Hook@....com>, Pu Wen <puwen@...on.cn>,
        Stephane Eranian <eranian@...gle.com>,
        Vince Weaver <vincent.weaver@...ne.edu>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH 1/2 RESEND3] perf/x86/amd/uncore: Do not set ThreadMask
 and SliceMask for non-L3 PMCs

On Fri, Jun 28, 2019 at 09:59:20PM +0000, Phillips, Kim wrote:
> From: Kim Phillips <kim.phillips@....com>
> 
> Commit d7cbbe49a930 ("perf/x86/amd/uncore: Set ThreadMask and SliceMask
> for L3 Cache perf events") enables L3 PMC events for all threads and
> slices by writing 1s in ChL3PmcCfg (L3 PMC PERF_CTL) register fields.
> 
> Those bitfields overlap with high order event select bits in the Data
> Fabric PMC control register, however.
> 
> So when a user requests raw Data Fabric events (-e amd_df/event=0xYYY/),
> the two highest order bits get inadvertently set, changing the counter
> select to events that don't exist, and for which no counts are read.
> 
> This patch changes the logic to write the L3 masks only when dealing
> with L3 PMC counters.
> 
> AMD Family 16h and below Northbridge (NB) counters were not affected.


Thanks!