[PATCH V2] powerpc/perf: Exclude pmc5/6 from the irrelevant PMU group constraints

[Madhavan Srinivasan]

On 9/21/20 12:40 PM, Athira Rajeev wrote:
> PMU counter support functions enforces event constraints for group of
> events to check if all events in a group can be monitored. Incase of
> event codes using PMC5 and PMC6 ( 500fa and 600f4 respectively ),
> not all constraints are applicable, say the threshold or sample bits.
> But current code includes pmc5 and pmc6 in some group constraints (like
> IC_DC Qualifier bits) which is actually not applicable and hence results
> in those events not getting counted when scheduled along with group of
> other events. Patch fixes this by excluding PMC5/6 from constraints
> which are not relevant for it.

Changes looks fine to me.

Reviewed-by: Madhavan Srinivasan <maddy at linux.ibm.com>

we need to CC this in Stable too.

> Fixes: 7ffd948 ("powerpc/perf: factor out power8 pmu functions")
> Signed-off-by: Athira Rajeev <atrajeev at linux.vnet.ibm.com>
> ---
> Changes in v2:
> - Added a block comment in the fix path explaining
>    why the change is needed.
>
>   arch/powerpc/perf/isa207-common.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
>
> diff --git a/arch/powerpc/perf/isa207-common.c b/arch/powerpc/perf/isa207-common.c
> index 964437a..12153da 100644
> --- a/arch/powerpc/perf/isa207-common.c
> +++ b/arch/powerpc/perf/isa207-common.c
> @@ -288,6 +288,15 @@ int isa207_get_constraint(u64 event, unsigned long *maskp, unsigned long *valp)
>
>   		mask  |= CNST_PMC_MASK(pmc);
>   		value |= CNST_PMC_VAL(pmc);
> +
> +		/*
> +		 * PMC5 and PMC6 are used to count cycles and instructions
> +		 * and these doesnot support most of the constraint bits.
> +		 * Add a check to exclude PMC5/6 from most of the constraints
> +		 * except for ebb/bhrb.
> +		 */
> +		if (pmc >= 5)
> +			goto ebb_bhrb;
>   	}
>
>   	if (pmc <= 4) {
> @@ -357,6 +366,7 @@ int isa207_get_constraint(u64 event, unsigned long *maskp, unsigned long *valp)
>   		}
>   	}
>
> +ebb_bhrb:
>   	if (!pmc && ebb)
>   		/* EBB events must specify the PMC */
>   		return -1;