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

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Message-ID: <fbf09b63-4b6d-ebdf-33fc-f93695b3f94a@linux.intel.com>
Date:   Mon, 20 Jul 2020 14:22:27 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
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 7/20/2020 12:20 PM, Peter Zijlstra wrote:
> 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.

I will fix the inaccurate description as below in V7.

+ * The pseudo umask-code is 0xX. The X equals the index of the fixed
+ * counter + 1, e.g., the fixed counter 2 has the pseudo-encoding 0x0300.

Thanks,
Kan