Date: Mon, 1 Jul 2024 18:06:02 +0100
From: Mark Rutland <mark.rutland@....com>
To: "Rob Herring (Arm)" <robh@...nel.org>
Cc: Russell King <linux@...linux.org.uk>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
	Oliver Upton <oliver.upton@...ux.dev>,
	James Morse <james.morse@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	Catalin Marinas <catalin.marinas@....com>,
	James Clark <james.clark@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org, kvmarm@...ts.linux.dev
Subject: Re: [PATCH v2 06/12] perf: arm_pmu: Remove event index to counter
 remapping

On Wed, Jun 26, 2024 at 04:32:30PM -0600, Rob Herring (Arm) wrote:
> Xscale and Armv6 PMUs defined the cycle counter at 0 and event counters
> starting at 1 and had 1:1 event index to counter numbering. On Armv7 and
> later, this changed the cycle counter to 31 and event counters start at
> 0. The drivers for Armv7 and PMUv3 kept the old event index numbering
> and introduced an event index to counter conversion. The conversion uses
> masking to convert from event index to a counter number. This operation
> relies on having at most 32 counters so that the cycle counter index 0
> can be transformed to counter number 31.
> 
> Armv9.4 adds support for an additional fixed function counter
> (instructions) which increases possible counters to more than 32, and
> the conversion won't work anymore as a simple subtract and mask. The
> primary reason for the translation (other than history) seems to be to
> have a contiguous mask of counters 0-N. Keeping that would result in
> more complicated index to counter conversions. Instead, store a mask of
> available counters rather than just number of events. That provides more
> information in addition to the number of events.
> 
> No (intended) functional changes.
> 
> Signed-off-by: Rob Herring (Arm) <robh@...nel.org>
> ---
> v2:
>  - Include Apple M1 PMU changes
>  - Use set_bit instead of bitmap_set(addr, bit, 1)
>  - Use for_each_andnot_bit() when clearing unused counters to avoid
>    accessing non-existent counters
>  - Use defines for XScale number of counters and
>    s/XSCALE_NUM_COUNTERS/XSCALE1_NUM_COUNTERS/
>  - Add and use define ARMV8_PMU_MAX_GENERAL_COUNTERS (copied from
>    tools/testing/selftests/kvm/aarch64/vpmu_counter_access.c)
> ---
>  arch/arm64/kvm/pmu-emul.c       |  6 ++--
>  drivers/perf/apple_m1_cpu_pmu.c |  4 +--
>  drivers/perf/arm_pmu.c          | 11 +++---
>  drivers/perf/arm_pmuv3.c        | 62 +++++++++++----------------------
>  drivers/perf/arm_v6_pmu.c       |  6 ++--
>  drivers/perf/arm_v7_pmu.c       | 77 ++++++++++++++++-------------------------
>  drivers/perf/arm_xscale_pmu.c   | 12 ++++---
>  include/linux/perf/arm_pmu.h    |  2 +-
>  include/linux/perf/arm_pmuv3.h  |  1 +
>  9 files changed, 75 insertions(+), 106 deletions(-)

FWIW, for this as-is:

Acked-by: Mark Rutland <mark.rutland@....com>

Mark.

> 
> diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
> index d1a476b08f54..69be070a9378 100644
> --- a/arch/arm64/kvm/pmu-emul.c
> +++ b/arch/arm64/kvm/pmu-emul.c
> @@ -910,10 +910,10 @@ u8 kvm_arm_pmu_get_max_counters(struct kvm *kvm)
>  	struct arm_pmu *arm_pmu = kvm->arch.arm_pmu;
>  
>  	/*
> -	 * The arm_pmu->num_events considers the cycle counter as well.
> -	 * Ignore that and return only the general-purpose counters.
> +	 * The arm_pmu->cntr_mask considers the fixed counter(s) as well.
> +	 * Ignore those and return only the general-purpose counters.
>  	 */
> -	return arm_pmu->num_events - 1;
> +	return bitmap_weight(arm_pmu->cntr_mask, ARMV8_PMU_MAX_GENERAL_COUNTERS);
>  }
>  
>  static void kvm_arm_set_pmu(struct kvm *kvm, struct arm_pmu *arm_pmu)
> diff --git a/drivers/perf/apple_m1_cpu_pmu.c b/drivers/perf/apple_m1_cpu_pmu.c
> index f322e5ca1114..c8f607912567 100644
> --- a/drivers/perf/apple_m1_cpu_pmu.c
> +++ b/drivers/perf/apple_m1_cpu_pmu.c
> @@ -400,7 +400,7 @@ static irqreturn_t m1_pmu_handle_irq(struct arm_pmu *cpu_pmu)
>  
>  	regs = get_irq_regs();
>  
> -	for (idx = 0; idx < cpu_pmu->num_events; idx++) {
> +	for_each_set_bit(idx, cpu_pmu->cntr_mask, M1_PMU_NR_COUNTERS) {
>  		struct perf_event *event = cpuc->events[idx];
>  		struct perf_sample_data data;
>  
> @@ -560,7 +560,7 @@ static int m1_pmu_init(struct arm_pmu *cpu_pmu, u32 flags)
>  	cpu_pmu->reset		  = m1_pmu_reset;
>  	cpu_pmu->set_event_filter = m1_pmu_set_event_filter;
>  
> -	cpu_pmu->num_events	  = M1_PMU_NR_COUNTERS;
> +	bitmap_set(cpu_pmu->cntr_mask, 0, M1_PMU_NR_COUNTERS);
>  	cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_EVENTS] = &m1_pmu_events_attr_group;
>  	cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_FORMATS] = &m1_pmu_format_attr_group;
>  	return 0;
> diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
> index 8458fe2cebb4..398cce3d76fc 100644
> --- a/drivers/perf/arm_pmu.c
> +++ b/drivers/perf/arm_pmu.c
> @@ -522,7 +522,7 @@ static void armpmu_enable(struct pmu *pmu)
>  {
>  	struct arm_pmu *armpmu = to_arm_pmu(pmu);
>  	struct pmu_hw_events *hw_events = this_cpu_ptr(armpmu->hw_events);
> -	bool enabled = !bitmap_empty(hw_events->used_mask, armpmu->num_events);
> +	bool enabled = !bitmap_empty(hw_events->used_mask, ARMPMU_MAX_HWEVENTS);
>  
>  	/* For task-bound events we may be called on other CPUs */
>  	if (!cpumask_test_cpu(smp_processor_id(), &armpmu->supported_cpus))
> @@ -742,7 +742,7 @@ static void cpu_pm_pmu_setup(struct arm_pmu *armpmu, unsigned long cmd)
>  	struct perf_event *event;
>  	int idx;
>  
> -	for (idx = 0; idx < armpmu->num_events; idx++) {
> +	for_each_set_bit(idx, armpmu->cntr_mask, ARMPMU_MAX_HWEVENTS) {
>  		event = hw_events->events[idx];
>  		if (!event)
>  			continue;
> @@ -772,7 +772,7 @@ static int cpu_pm_pmu_notify(struct notifier_block *b, unsigned long cmd,
>  {
>  	struct arm_pmu *armpmu = container_of(b, struct arm_pmu, cpu_pm_nb);
>  	struct pmu_hw_events *hw_events = this_cpu_ptr(armpmu->hw_events);
> -	bool enabled = !bitmap_empty(hw_events->used_mask, armpmu->num_events);
> +	bool enabled = !bitmap_empty(hw_events->used_mask, ARMPMU_MAX_HWEVENTS);
>  
>  	if (!cpumask_test_cpu(smp_processor_id(), &armpmu->supported_cpus))
>  		return NOTIFY_DONE;
> @@ -924,8 +924,9 @@ int armpmu_register(struct arm_pmu *pmu)
>  	if (ret)
>  		goto out_destroy;
>  
> -	pr_info("enabled with %s PMU driver, %d counters available%s\n",
> -		pmu->name, pmu->num_events,
> +	pr_info("enabled with %s PMU driver, %d (%*pb) counters available%s\n",
> +		pmu->name, bitmap_weight(pmu->cntr_mask, ARMPMU_MAX_HWEVENTS),
> +		ARMPMU_MAX_HWEVENTS, &pmu->cntr_mask,
>  		has_nmi ? ", using NMIs" : "");
>  
>  	kvm_host_pmu_init(pmu);
> diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
> index 6cbd37fd691a..53ad674bf009 100644
> --- a/drivers/perf/arm_pmuv3.c
> +++ b/drivers/perf/arm_pmuv3.c
> @@ -454,9 +454,7 @@ static const struct attribute_group armv8_pmuv3_caps_attr_group = {
>  /*
>   * Perf Events' indices
>   */
> -#define	ARMV8_IDX_CYCLE_COUNTER	0
> -#define	ARMV8_IDX_COUNTER0	1
> -#define	ARMV8_IDX_CYCLE_COUNTER_USER	32
> +#define	ARMV8_IDX_CYCLE_COUNTER	31
>  
>  /*
>   * We unconditionally enable ARMv8.5-PMU long event counter support
> @@ -489,19 +487,12 @@ static bool armv8pmu_event_is_chained(struct perf_event *event)
>  	return !armv8pmu_event_has_user_read(event) &&
>  	       armv8pmu_event_is_64bit(event) &&
>  	       !armv8pmu_has_long_event(cpu_pmu) &&
> -	       (idx != ARMV8_IDX_CYCLE_COUNTER);
> +	       (idx <= ARMV8_PMU_MAX_GENERAL_COUNTERS);
>  }
>  
>  /*
>   * ARMv8 low level PMU access
>   */
> -
> -/*
> - * Perf Event to low level counters mapping
> - */
> -#define	ARMV8_IDX_TO_COUNTER(x)	\
> -	(((x) - ARMV8_IDX_COUNTER0) & ARMV8_PMU_COUNTER_MASK)
> -
>  static u64 armv8pmu_pmcr_read(void)
>  {
>  	return read_pmcr();
> @@ -521,14 +512,12 @@ static int armv8pmu_has_overflowed(u32 pmovsr)
>  
>  static int armv8pmu_counter_has_overflowed(u32 pmnc, int idx)
>  {
> -	return pmnc & BIT(ARMV8_IDX_TO_COUNTER(idx));
> +	return pmnc & BIT(idx);
>  }
>  
>  static u64 armv8pmu_read_evcntr(int idx)
>  {
> -	u32 counter = ARMV8_IDX_TO_COUNTER(idx);
> -
> -	return read_pmevcntrn(counter);
> +	return read_pmevcntrn(idx);
>  }
>  
>  static u64 armv8pmu_read_hw_counter(struct perf_event *event)
> @@ -557,7 +546,7 @@ static bool armv8pmu_event_needs_bias(struct perf_event *event)
>  		return false;
>  
>  	if (armv8pmu_has_long_event(cpu_pmu) ||
> -	    idx == ARMV8_IDX_CYCLE_COUNTER)
> +	    idx >= ARMV8_PMU_MAX_GENERAL_COUNTERS)
>  		return true;
>  
>  	return false;
> @@ -595,9 +584,7 @@ static u64 armv8pmu_read_counter(struct perf_event *event)
>  
>  static void armv8pmu_write_evcntr(int idx, u64 value)
>  {
> -	u32 counter = ARMV8_IDX_TO_COUNTER(idx);
> -
> -	write_pmevcntrn(counter, value);
> +	write_pmevcntrn(idx, value);
>  }
>  
>  static void armv8pmu_write_hw_counter(struct perf_event *event,
> @@ -628,7 +615,6 @@ static void armv8pmu_write_counter(struct perf_event *event, u64 value)
>  
>  static void armv8pmu_write_evtype(int idx, unsigned long val)
>  {
> -	u32 counter = ARMV8_IDX_TO_COUNTER(idx);
>  	unsigned long mask = ARMV8_PMU_EVTYPE_EVENT |
>  			     ARMV8_PMU_INCLUDE_EL2 |
>  			     ARMV8_PMU_EXCLUDE_EL0 |
> @@ -638,7 +624,7 @@ static void armv8pmu_write_evtype(int idx, unsigned long val)
>  		mask |= ARMV8_PMU_EVTYPE_TC | ARMV8_PMU_EVTYPE_TH;
>  
>  	val &= mask;
> -	write_pmevtypern(counter, val);
> +	write_pmevtypern(idx, val);
>  }
>  
>  static void armv8pmu_write_event_type(struct perf_event *event)
> @@ -667,7 +653,7 @@ static void armv8pmu_write_event_type(struct perf_event *event)
>  
>  static u32 armv8pmu_event_cnten_mask(struct perf_event *event)
>  {
> -	int counter = ARMV8_IDX_TO_COUNTER(event->hw.idx);
> +	int counter = event->hw.idx;
>  	u32 mask = BIT(counter);
>  
>  	if (armv8pmu_event_is_chained(event))
> @@ -726,8 +712,7 @@ static void armv8pmu_enable_intens(u32 mask)
>  
>  static void armv8pmu_enable_event_irq(struct perf_event *event)
>  {
> -	u32 counter = ARMV8_IDX_TO_COUNTER(event->hw.idx);
> -	armv8pmu_enable_intens(BIT(counter));
> +	armv8pmu_enable_intens(BIT(event->hw.idx));
>  }
>  
>  static void armv8pmu_disable_intens(u32 mask)
> @@ -741,8 +726,7 @@ static void armv8pmu_disable_intens(u32 mask)
>  
>  static void armv8pmu_disable_event_irq(struct perf_event *event)
>  {
> -	u32 counter = ARMV8_IDX_TO_COUNTER(event->hw.idx);
> -	armv8pmu_disable_intens(BIT(counter));
> +	armv8pmu_disable_intens(BIT(event->hw.idx));
>  }
>  
>  static u32 armv8pmu_getreset_flags(void)
> @@ -786,7 +770,8 @@ static void armv8pmu_enable_user_access(struct arm_pmu *cpu_pmu)
>  	struct pmu_hw_events *cpuc = this_cpu_ptr(cpu_pmu->hw_events);
>  
>  	/* Clear any unused counters to avoid leaking their contents */
> -	for_each_clear_bit(i, cpuc->used_mask, cpu_pmu->num_events) {
> +	for_each_andnot_bit(i, cpu_pmu->cntr_mask, cpuc->used_mask,
> +			    ARMPMU_MAX_HWEVENTS) {
>  		if (i == ARMV8_IDX_CYCLE_COUNTER)
>  			write_pmccntr(0);
>  		else
> @@ -869,7 +854,7 @@ static irqreturn_t armv8pmu_handle_irq(struct arm_pmu *cpu_pmu)
>  	 * to prevent skews in group events.
>  	 */
>  	armv8pmu_stop(cpu_pmu);
> -	for (idx = 0; idx < cpu_pmu->num_events; ++idx) {
> +	for_each_set_bit(idx, cpu_pmu->cntr_mask, ARMPMU_MAX_HWEVENTS) {
>  		struct perf_event *event = cpuc->events[idx];
>  		struct hw_perf_event *hwc;
>  
> @@ -908,7 +893,7 @@ static int armv8pmu_get_single_idx(struct pmu_hw_events *cpuc,
>  {
>  	int idx;
>  
> -	for (idx = ARMV8_IDX_COUNTER0; idx < cpu_pmu->num_events; idx++) {
> +	for_each_set_bit(idx, cpu_pmu->cntr_mask, ARMV8_PMU_MAX_GENERAL_COUNTERS) {
>  		if (!test_and_set_bit(idx, cpuc->used_mask))
>  			return idx;
>  	}
> @@ -924,7 +909,9 @@ static int armv8pmu_get_chain_idx(struct pmu_hw_events *cpuc,
>  	 * Chaining requires two consecutive event counters, where
>  	 * the lower idx must be even.
>  	 */
> -	for (idx = ARMV8_IDX_COUNTER0 + 1; idx < cpu_pmu->num_events; idx += 2) {
> +	for_each_set_bit(idx, cpu_pmu->cntr_mask, ARMV8_PMU_MAX_GENERAL_COUNTERS) {
> +		if (!(idx & 0x1))
> +			continue;
>  		if (!test_and_set_bit(idx, cpuc->used_mask)) {
>  			/* Check if the preceding even counter is available */
>  			if (!test_and_set_bit(idx - 1, cpuc->used_mask))
> @@ -978,15 +965,7 @@ static int armv8pmu_user_event_idx(struct perf_event *event)
>  	if (!sysctl_perf_user_access || !armv8pmu_event_has_user_read(event))
>  		return 0;
>  
> -	/*
> -	 * We remap the cycle counter index to 32 to
> -	 * match the offset applied to the rest of
> -	 * the counter indices.
> -	 */
> -	if (event->hw.idx == ARMV8_IDX_CYCLE_COUNTER)
> -		return ARMV8_IDX_CYCLE_COUNTER_USER;
> -
> -	return event->hw.idx;
> +	return event->hw.idx + 1;
>  }
>  
>  /*
> @@ -1211,10 +1190,11 @@ static void __armv8pmu_probe_pmu(void *info)
>  	probe->present = true;
>  
>  	/* Read the nb of CNTx counters supported from PMNC */
> -	cpu_pmu->num_events = FIELD_GET(ARMV8_PMU_PMCR_N, armv8pmu_pmcr_read());
> +	bitmap_set(cpu_pmu->cntr_mask,
> +		   0, FIELD_GET(ARMV8_PMU_PMCR_N, armv8pmu_pmcr_read()));
>  
>  	/* Add the CPU cycles counter */
> -	cpu_pmu->num_events += 1;
> +	set_bit(ARMV8_IDX_CYCLE_COUNTER, cpu_pmu->cntr_mask);
>  
>  	pmceid[0] = pmceid_raw[0] = read_pmceid0();
>  	pmceid[1] = pmceid_raw[1] = read_pmceid1();
> diff --git a/drivers/perf/arm_v6_pmu.c b/drivers/perf/arm_v6_pmu.c
> index 0bb685b4bac5..b09615bb2bb2 100644
> --- a/drivers/perf/arm_v6_pmu.c
> +++ b/drivers/perf/arm_v6_pmu.c
> @@ -64,6 +64,7 @@ enum armv6_counters {
>  	ARMV6_CYCLE_COUNTER = 0,
>  	ARMV6_COUNTER0,
>  	ARMV6_COUNTER1,
> +	ARMV6_NUM_COUNTERS
>  };
>  
>  /*
> @@ -254,7 +255,7 @@ armv6pmu_handle_irq(struct arm_pmu *cpu_pmu)
>  	 */
>  	armv6_pmcr_write(pmcr);
>  
> -	for (idx = 0; idx < cpu_pmu->num_events; ++idx) {
> +	for_each_set_bit(idx, cpu_pmu->cntr_mask, ARMV6_NUM_COUNTERS) {
>  		struct perf_event *event = cpuc->events[idx];
>  		struct hw_perf_event *hwc;
>  
> @@ -391,7 +392,8 @@ static void armv6pmu_init(struct arm_pmu *cpu_pmu)
>  	cpu_pmu->start		= armv6pmu_start;
>  	cpu_pmu->stop		= armv6pmu_stop;
>  	cpu_pmu->map_event	= armv6_map_event;
> -	cpu_pmu->num_events	= 3;
> +
> +	bitmap_set(cpu_pmu->cntr_mask, 0, ARMV6_NUM_COUNTERS);
>  }
>  
>  static int armv6_1136_pmu_init(struct arm_pmu *cpu_pmu)
> diff --git a/drivers/perf/arm_v7_pmu.c b/drivers/perf/arm_v7_pmu.c
> index 928ac3d626ed..420cadd108e7 100644
> --- a/drivers/perf/arm_v7_pmu.c
> +++ b/drivers/perf/arm_v7_pmu.c
> @@ -649,24 +649,12 @@ static struct attribute_group armv7_pmuv2_events_attr_group = {
>  /*
>   * Perf Events' indices
>   */
> -#define	ARMV7_IDX_CYCLE_COUNTER	0
> -#define	ARMV7_IDX_COUNTER0	1
> -#define	ARMV7_IDX_COUNTER_LAST(cpu_pmu) \
> -	(ARMV7_IDX_CYCLE_COUNTER + cpu_pmu->num_events - 1)
> -
> -#define	ARMV7_MAX_COUNTERS	32
> -#define	ARMV7_COUNTER_MASK	(ARMV7_MAX_COUNTERS - 1)
> -
> +#define	ARMV7_IDX_CYCLE_COUNTER	31
> +#define	ARMV7_IDX_COUNTER_MAX	31
>  /*
>   * ARMv7 low level PMNC access
>   */
>  
> -/*
> - * Perf Event to low level counters mapping
> - */
> -#define	ARMV7_IDX_TO_COUNTER(x)	\
> -	(((x) - ARMV7_IDX_COUNTER0) & ARMV7_COUNTER_MASK)
> -
>  /*
>   * Per-CPU PMNC: config reg
>   */
> @@ -725,19 +713,17 @@ static inline int armv7_pmnc_has_overflowed(u32 pmnc)
>  
>  static inline int armv7_pmnc_counter_valid(struct arm_pmu *cpu_pmu, int idx)
>  {
> -	return idx >= ARMV7_IDX_CYCLE_COUNTER &&
> -		idx <= ARMV7_IDX_COUNTER_LAST(cpu_pmu);
> +	return test_bit(idx, cpu_pmu->cntr_mask);
>  }
>  
>  static inline int armv7_pmnc_counter_has_overflowed(u32 pmnc, int idx)
>  {
> -	return pmnc & BIT(ARMV7_IDX_TO_COUNTER(idx));
> +	return pmnc & BIT(idx);
>  }
>  
>  static inline void armv7_pmnc_select_counter(int idx)
>  {
> -	u32 counter = ARMV7_IDX_TO_COUNTER(idx);
> -	asm volatile("mcr p15, 0, %0, c9, c12, 5" : : "r" (counter));
> +	asm volatile("mcr p15, 0, %0, c9, c12, 5" : : "r" (idx));
>  	isb();
>  }
>  
> @@ -787,29 +773,25 @@ static inline void armv7_pmnc_write_evtsel(int idx, u32 val)
>  
>  static inline void armv7_pmnc_enable_counter(int idx)
>  {
> -	u32 counter = ARMV7_IDX_TO_COUNTER(idx);
> -	asm volatile("mcr p15, 0, %0, c9, c12, 1" : : "r" (BIT(counter)));
> +	asm volatile("mcr p15, 0, %0, c9, c12, 1" : : "r" (BIT(idx)));
>  }
>  
>  static inline void armv7_pmnc_disable_counter(int idx)
>  {
> -	u32 counter = ARMV7_IDX_TO_COUNTER(idx);
> -	asm volatile("mcr p15, 0, %0, c9, c12, 2" : : "r" (BIT(counter)));
> +	asm volatile("mcr p15, 0, %0, c9, c12, 2" : : "r" (BIT(idx)));
>  }
>  
>  static inline void armv7_pmnc_enable_intens(int idx)
>  {
> -	u32 counter = ARMV7_IDX_TO_COUNTER(idx);
> -	asm volatile("mcr p15, 0, %0, c9, c14, 1" : : "r" (BIT(counter)));
> +	asm volatile("mcr p15, 0, %0, c9, c14, 1" : : "r" (BIT(idx)));
>  }
>  
>  static inline void armv7_pmnc_disable_intens(int idx)
>  {
> -	u32 counter = ARMV7_IDX_TO_COUNTER(idx);
> -	asm volatile("mcr p15, 0, %0, c9, c14, 2" : : "r" (BIT(counter)));
> +	asm volatile("mcr p15, 0, %0, c9, c14, 2" : : "r" (BIT(idx)));
>  	isb();
>  	/* Clear the overflow flag in case an interrupt is pending. */
> -	asm volatile("mcr p15, 0, %0, c9, c12, 3" : : "r" (BIT(counter)));
> +	asm volatile("mcr p15, 0, %0, c9, c12, 3" : : "r" (BIT(idx)));
>  	isb();
>  }
>  
> @@ -853,15 +835,12 @@ static void armv7_pmnc_dump_regs(struct arm_pmu *cpu_pmu)
>  	asm volatile("mrc p15, 0, %0, c9, c13, 0" : "=r" (val));
>  	pr_info("CCNT  =0x%08x\n", val);
>  
> -	for (cnt = ARMV7_IDX_COUNTER0;
> -			cnt <= ARMV7_IDX_COUNTER_LAST(cpu_pmu); cnt++) {
> +	for_each_set_bit(cnt, cpu_pmu->cntr_mask, ARMV7_IDX_COUNTER_MAX) {
>  		armv7_pmnc_select_counter(cnt);
>  		asm volatile("mrc p15, 0, %0, c9, c13, 2" : "=r" (val));
> -		pr_info("CNT[%d] count =0x%08x\n",
> -			ARMV7_IDX_TO_COUNTER(cnt), val);
> +		pr_info("CNT[%d] count =0x%08x\n", cnt, val);
>  		asm volatile("mrc p15, 0, %0, c9, c13, 1" : "=r" (val));
> -		pr_info("CNT[%d] evtsel=0x%08x\n",
> -			ARMV7_IDX_TO_COUNTER(cnt), val);
> +		pr_info("CNT[%d] evtsel=0x%08x\n", cnt, val);
>  	}
>  }
>  #endif
> @@ -958,7 +937,7 @@ static irqreturn_t armv7pmu_handle_irq(struct arm_pmu *cpu_pmu)
>  	 */
>  	regs = get_irq_regs();
>  
> -	for (idx = 0; idx < cpu_pmu->num_events; ++idx) {
> +	for_each_set_bit(idx, cpu_pmu->cntr_mask, ARMPMU_MAX_HWEVENTS) {
>  		struct perf_event *event = cpuc->events[idx];
>  		struct hw_perf_event *hwc;
>  
> @@ -1027,7 +1006,7 @@ static int armv7pmu_get_event_idx(struct pmu_hw_events *cpuc,
>  	 * For anything other than a cycle counter, try and use
>  	 * the events counters
>  	 */
> -	for (idx = ARMV7_IDX_COUNTER0; idx < cpu_pmu->num_events; ++idx) {
> +	for_each_set_bit(idx, cpu_pmu->cntr_mask, ARMV7_IDX_COUNTER_MAX) {
>  		if (!test_and_set_bit(idx, cpuc->used_mask))
>  			return idx;
>  	}
> @@ -1073,7 +1052,7 @@ static int armv7pmu_set_event_filter(struct hw_perf_event *event,
>  static void armv7pmu_reset(void *info)
>  {
>  	struct arm_pmu *cpu_pmu = (struct arm_pmu *)info;
> -	u32 idx, nb_cnt = cpu_pmu->num_events, val;
> +	u32 idx, val;
>  
>  	if (cpu_pmu->secure_access) {
>  		asm volatile("mrc p15, 0, %0, c1, c1, 1" : "=r" (val));
> @@ -1082,7 +1061,7 @@ static void armv7pmu_reset(void *info)
>  	}
>  
>  	/* The counter and interrupt enable registers are unknown at reset. */
> -	for (idx = ARMV7_IDX_CYCLE_COUNTER; idx < nb_cnt; ++idx) {
> +	for_each_set_bit(idx, cpu_pmu->cntr_mask, ARMPMU_MAX_HWEVENTS) {
>  		armv7_pmnc_disable_counter(idx);
>  		armv7_pmnc_disable_intens(idx);
>  	}
> @@ -1161,20 +1140,22 @@ static void armv7pmu_init(struct arm_pmu *cpu_pmu)
>  
>  static void armv7_read_num_pmnc_events(void *info)
>  {
> -	int *nb_cnt = info;
> +	int nb_cnt;
> +	struct arm_pmu *cpu_pmu = info;
>  
>  	/* Read the nb of CNTx counters supported from PMNC */
> -	*nb_cnt = (armv7_pmnc_read() >> ARMV7_PMNC_N_SHIFT) & ARMV7_PMNC_N_MASK;
> +	nb_cnt = (armv7_pmnc_read() >> ARMV7_PMNC_N_SHIFT) & ARMV7_PMNC_N_MASK;
> +	bitmap_set(cpu_pmu->cntr_mask, 0, nb_cnt);
>  
>  	/* Add the CPU cycles counter */
> -	*nb_cnt += 1;
> +	set_bit(ARMV7_IDX_CYCLE_COUNTER, cpu_pmu->cntr_mask);
>  }
>  
>  static int armv7_probe_num_events(struct arm_pmu *arm_pmu)
>  {
>  	return smp_call_function_any(&arm_pmu->supported_cpus,
>  				     armv7_read_num_pmnc_events,
> -				     &arm_pmu->num_events, 1);
> +				     arm_pmu, 1);
>  }
>  
>  static int armv7_a8_pmu_init(struct arm_pmu *cpu_pmu)
> @@ -1524,7 +1505,7 @@ static void krait_pmu_reset(void *info)
>  {
>  	u32 vval, fval;
>  	struct arm_pmu *cpu_pmu = info;
> -	u32 idx, nb_cnt = cpu_pmu->num_events;
> +	u32 idx;
>  
>  	armv7pmu_reset(info);
>  
> @@ -1538,7 +1519,7 @@ static void krait_pmu_reset(void *info)
>  	venum_post_pmresr(vval, fval);
>  
>  	/* Reset PMxEVNCTCR to sane default */
> -	for (idx = ARMV7_IDX_CYCLE_COUNTER; idx < nb_cnt; ++idx) {
> +	for_each_set_bit(idx, cpu_pmu->cntr_mask, ARMV7_IDX_COUNTER_MAX) {
>  		armv7_pmnc_select_counter(idx);
>  		asm volatile("mcr p15, 0, %0, c9, c15, 0" : : "r" (0));
>  	}
> @@ -1562,7 +1543,7 @@ static int krait_event_to_bit(struct perf_event *event, unsigned int region,
>  	 * Lower bits are reserved for use by the counters (see
>  	 * armv7pmu_get_event_idx() for more info)
>  	 */
> -	bit += ARMV7_IDX_COUNTER_LAST(cpu_pmu) + 1;
> +	bit += bitmap_weight(cpu_pmu->cntr_mask, ARMV7_IDX_COUNTER_MAX);
>  
>  	return bit;
>  }
> @@ -1845,7 +1826,7 @@ static void scorpion_pmu_reset(void *info)
>  {
>  	u32 vval, fval;
>  	struct arm_pmu *cpu_pmu = info;
> -	u32 idx, nb_cnt = cpu_pmu->num_events;
> +	u32 idx;
>  
>  	armv7pmu_reset(info);
>  
> @@ -1860,7 +1841,7 @@ static void scorpion_pmu_reset(void *info)
>  	venum_post_pmresr(vval, fval);
>  
>  	/* Reset PMxEVNCTCR to sane default */
> -	for (idx = ARMV7_IDX_CYCLE_COUNTER; idx < nb_cnt; ++idx) {
> +	for_each_set_bit(idx, cpu_pmu->cntr_mask, ARMV7_IDX_COUNTER_MAX) {
>  		armv7_pmnc_select_counter(idx);
>  		asm volatile("mcr p15, 0, %0, c9, c15, 0" : : "r" (0));
>  	}
> @@ -1883,7 +1864,7 @@ static int scorpion_event_to_bit(struct perf_event *event, unsigned int region,
>  	 * Lower bits are reserved for use by the counters (see
>  	 * armv7pmu_get_event_idx() for more info)
>  	 */
> -	bit += ARMV7_IDX_COUNTER_LAST(cpu_pmu) + 1;
> +	bit += bitmap_weight(cpu_pmu->cntr_mask, ARMV7_IDX_COUNTER_MAX);
>  
>  	return bit;
>  }
> diff --git a/drivers/perf/arm_xscale_pmu.c b/drivers/perf/arm_xscale_pmu.c
> index 3d8b72d6b37f..638fea9b1263 100644
> --- a/drivers/perf/arm_xscale_pmu.c
> +++ b/drivers/perf/arm_xscale_pmu.c
> @@ -53,6 +53,8 @@ enum xscale_counters {
>  	XSCALE_COUNTER2,
>  	XSCALE_COUNTER3,
>  };
> +#define XSCALE1_NUM_COUNTERS	3
> +#define XSCALE2_NUM_COUNTERS	5
>  
>  static const unsigned xscale_perf_map[PERF_COUNT_HW_MAX] = {
>  	PERF_MAP_ALL_UNSUPPORTED,
> @@ -168,7 +170,7 @@ xscale1pmu_handle_irq(struct arm_pmu *cpu_pmu)
>  
>  	regs = get_irq_regs();
>  
> -	for (idx = 0; idx < cpu_pmu->num_events; ++idx) {
> +	for_each_set_bit(idx, cpu_pmu->cntr_mask, XSCALE1_NUM_COUNTERS) {
>  		struct perf_event *event = cpuc->events[idx];
>  		struct hw_perf_event *hwc;
>  
> @@ -364,7 +366,8 @@ static int xscale1pmu_init(struct arm_pmu *cpu_pmu)
>  	cpu_pmu->start		= xscale1pmu_start;
>  	cpu_pmu->stop		= xscale1pmu_stop;
>  	cpu_pmu->map_event	= xscale_map_event;
> -	cpu_pmu->num_events	= 3;
> +
> +	bitmap_set(cpu_pmu->cntr_mask, 0, XSCALE1_NUM_COUNTERS);
>  
>  	return 0;
>  }
> @@ -500,7 +503,7 @@ xscale2pmu_handle_irq(struct arm_pmu *cpu_pmu)
>  
>  	regs = get_irq_regs();
>  
> -	for (idx = 0; idx < cpu_pmu->num_events; ++idx) {
> +	for_each_set_bit(idx, cpu_pmu->cntr_mask, XSCALE2_NUM_COUNTERS) {
>  		struct perf_event *event = cpuc->events[idx];
>  		struct hw_perf_event *hwc;
>  
> @@ -719,7 +722,8 @@ static int xscale2pmu_init(struct arm_pmu *cpu_pmu)
>  	cpu_pmu->start		= xscale2pmu_start;
>  	cpu_pmu->stop		= xscale2pmu_stop;
>  	cpu_pmu->map_event	= xscale_map_event;
> -	cpu_pmu->num_events	= 5;
> +
> +	bitmap_set(cpu_pmu->cntr_mask, 0, XSCALE2_NUM_COUNTERS);
>  
>  	return 0;
>  }
> diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h
> index b3b34f6670cf..e5d6d204beab 100644
> --- a/include/linux/perf/arm_pmu.h
> +++ b/include/linux/perf/arm_pmu.h
> @@ -96,7 +96,7 @@ struct arm_pmu {
>  	void		(*stop)(struct arm_pmu *);
>  	void		(*reset)(void *);
>  	int		(*map_event)(struct perf_event *event);
> -	int		num_events;
> +	DECLARE_BITMAP(cntr_mask, ARMPMU_MAX_HWEVENTS);
>  	bool		secure_access; /* 32-bit ARM only */
>  #define ARMV8_PMUV3_MAX_COMMON_EVENTS		0x40
>  	DECLARE_BITMAP(pmceid_bitmap, ARMV8_PMUV3_MAX_COMMON_EVENTS);
> diff --git a/include/linux/perf/arm_pmuv3.h b/include/linux/perf/arm_pmuv3.h
> index 7867db04ec98..eccbdd8eb98f 100644
> --- a/include/linux/perf/arm_pmuv3.h
> +++ b/include/linux/perf/arm_pmuv3.h
> @@ -6,6 +6,7 @@
>  #ifndef __PERF_ARM_PMUV3_H
>  #define __PERF_ARM_PMUV3_H
>  
> +#define ARMV8_PMU_MAX_GENERAL_COUNTERS	31
>  #define ARMV8_PMU_MAX_COUNTERS	32
>  #define ARMV8_PMU_COUNTER_MASK	(ARMV8_PMU_MAX_COUNTERS - 1)
>  
> 
> -- 
> 2.43.0
> 

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