Re: [PATCH v3 1/2] powerpc/perf: Infrastructure to support checking of attr.config*

[Athira Rajeev <atrajeev@linux.vnet.ibm.com>]

> On 25-Mar-2021, at 5:23 PM, Madhavan Srinivasan <maddy@linux.ibm.com> wrote:
> 
> Introduce code to support the checking of attr.config* for
> values which are reserved for a given platform.
> Performance Monitoring Unit (PMU) configuration registers
> have fields that are reserved and some specific values for
> bit fields are reserved. For ex., MMCRA[61:62] is
> Random Sampling Mode (SM) and value of 0b11 for this field
> is reserved.
> 
> Writing non-zero or invalid values in these fields will
> have unknown behaviours.
> 
> Patch adds a generic call-back function "check_attr_config"
> in "struct power_pmu", to be called in event_init to
> check for attr.config* values for a given platform.
> "check_attr_config" is valid only for raw event type.
> 
> Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
> ---
> Changelog v2:
> -Fixed commit message
> 
> Changelog v1:
> -Fixed commit message and in-code comments

Changes looks fine to me.

Reviewed-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>

Thanks,
Athira
> 
> arch/powerpc/include/asm/perf_event_server.h |  6 ++++++
> arch/powerpc/perf/core-book3s.c              | 14 ++++++++++++++
> 2 files changed, 20 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/perf_event_server.h b/arch/powerpc/include/asm/perf_event_server.h
> index 00e7e671bb4b..dde97d7d9253 100644
> --- a/arch/powerpc/include/asm/perf_event_server.h
> +++ b/arch/powerpc/include/asm/perf_event_server.h
> @@ -67,6 +67,12 @@ struct power_pmu {
> 	 * the pmu supports extended perf regs capability
> 	 */
> 	int		capabilities;
> +	/*
> +	 * Function to check event code for values which are
> +	 * reserved. Function takes struct perf_event as input,
> +	 * since event code could be spread in attr.config*
> +	 */
> +	int		(*check_attr_config)(struct perf_event *ev);
> };
> 
> /*
> diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
> index 6817331e22ff..c6eeb4fdc5fd 100644
> --- a/arch/powerpc/perf/core-book3s.c
> +++ b/arch/powerpc/perf/core-book3s.c
> @@ -1958,6 +1958,20 @@ static int power_pmu_event_init(struct perf_event *event)
> 
> 		if (ppmu->blacklist_ev && is_event_blacklisted(ev))
> 			return -EINVAL;
> +		/*
> +		 * PMU config registers have fields that are
> +		 * reserved and specific value to bit field as reserved.
> +		 * For ex., MMCRA[61:62] is Randome Sampling Mode (SM)
> +		 * and value of 0b11 to this field is reserved.
> +		 *
> +		 * This check is needed only for raw event type,
> +		 * since tools like fuzzer use raw event type to
> +		 * provide randomized event code values for test.
> +		 *
> +		 */
> +		if (ppmu->check_attr_config &&
> +		    ppmu->check_attr_config(event))
> +			return -EINVAL;
> 		break;
> 	default:
> 		return -ENOENT;
> -- 
> 2.26.2
>