linux-kernel - Re: [PATCH V6 03/14] perf/x86/intel: Introduce the fourth fixed counter

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Message-ID: <20200720162024.GT10769@hirez.programming.kicks-ass.net>
Date:   Mon, 20 Jul 2020 18:20:24 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     kan.liang@...ux.intel.com
Cc:     acme@...hat.com, mingo@...nel.org, linux-kernel@...r.kernel.org,
        jolsa@...nel.org, eranian@...gle.com,
        alexander.shishkin@...ux.intel.com, ak@...ux.intel.com
Subject: Re: [PATCH V6 03/14] perf/x86/intel: Introduce the fourth fixed
 counter

On Fri, Jul 17, 2020 at 07:05:43AM -0700, kan.liang@...ux.intel.com wrote:
>  /*
> + * There is no event-code assigned to the fixed-mode PMCs.
> + *
> + * For a fixed-mode PMC, which has an equivalent event on a general-purpose
> + * PMC, the event-code of the equivalent event is used for the fixed-mode PMC,
> + * e.g., Instr_Retired.Any and CPU_CLK_Unhalted.Core.
> + *
> + * For a fixed-mode PMC, which doesn't have an equivalent event, a
> + * pseudo-encoding is used, e.g., CPU_CLK_Unhalted.Ref and TOPDOWN.SLOTS.
> + * The pseudo event-code for a fixed-mode PMC must be 0x00.
> + * The pseudo umask-code is 0x0X. The X indicates the index of the fixed
> + * counter.

Isn't it X+1 ? Such that 0x0000 is an invalid event? After all, the
pseudo event for Fixed2 is 0x0300.

> + *
> + * The counts are available in separate MSRs:
>   */