arm64: perf: Clean up enable/disable calls

Reading this code bordered on painful, what with all the repetition and
pointless return values. More fundamentally, dribbling the hardware
enables and disables in one bit at a time incurs needless system
register overhead for chained events and on reset. We already use
bitmask values for the KVM hooks, so consolidate all the register
accesses to match, and make a reasonable saving in both source and
object code.

Signed-off-by: Robin Murphy <[e-mail]>
Signed-off-by: Will Deacon <[e-mail]>

arch/arm64/kernel/perf_event.c

···
 	}
 }
 
-static inline int armv8pmu_enable_counter(int idx)
+static u32 armv8pmu_event_cnten_mask(struct perf_event *event)
 {
-	u32 counter = ARMV8_IDX_TO_COUNTER(idx);
-	write_sysreg(BIT(counter), pmcntenset_el0);
-	return idx;
+	int counter = ARMV8_IDX_TO_COUNTER(event->hw.idx);
+	u32 mask = BIT(counter);
+
+	if (armv8pmu_event_is_chained(event))
+		mask |= BIT(counter - 1);
+	return mask;
+}
+
+static inline void armv8pmu_enable_counter(u32 mask)
+{
+	write_sysreg(mask, pmcntenset_el0);
 }
 
 static inline void armv8pmu_enable_event_counter(struct perf_event *event)
 {
 	struct perf_event_attr *attr = &event->attr;
-	int idx = event->hw.idx;
-	u32 counter_bits = BIT(ARMV8_IDX_TO_COUNTER(idx));
+	u32 mask = armv8pmu_event_cnten_mask(event);
 
-	if (armv8pmu_event_is_chained(event))
-		counter_bits |= BIT(ARMV8_IDX_TO_COUNTER(idx - 1));
-
-	kvm_set_pmu_events(counter_bits, attr);
+	kvm_set_pmu_events(mask, attr);
 
 	/* We rely on the hypervisor switch code to enable guest counters */
-	if (!kvm_pmu_counter_deferred(attr)) {
-		armv8pmu_enable_counter(idx);
-		if (armv8pmu_event_is_chained(event))
-			armv8pmu_enable_counter(idx - 1);
-	}
+	if (!kvm_pmu_counter_deferred(attr))
+		armv8pmu_enable_counter(mask);
 }
 
-static inline int armv8pmu_disable_counter(int idx)
+static inline void armv8pmu_disable_counter(u32 mask)
 {
-	u32 counter = ARMV8_IDX_TO_COUNTER(idx);
-	write_sysreg(BIT(counter), pmcntenclr_el0);
-	return idx;
+	write_sysreg(mask, pmcntenclr_el0);
 }
 
 static inline void armv8pmu_disable_event_counter(struct perf_event *event)
 {
-	struct hw_perf_event *hwc = &event->hw;
 	struct perf_event_attr *attr = &event->attr;
-	int idx = hwc->idx;
-	u32 counter_bits = BIT(ARMV8_IDX_TO_COUNTER(idx));
+	u32 mask = armv8pmu_event_cnten_mask(event);
 
-	if (armv8pmu_event_is_chained(event))
-		counter_bits |= BIT(ARMV8_IDX_TO_COUNTER(idx - 1));
-
-	kvm_clr_pmu_events(counter_bits);
+	kvm_clr_pmu_events(mask);
 
 	/* We rely on the hypervisor switch code to disable guest counters */
-	if (!kvm_pmu_counter_deferred(attr)) {
-		if (armv8pmu_event_is_chained(event))
-			armv8pmu_disable_counter(idx - 1);
-		armv8pmu_disable_counter(idx);
-	}
+	if (!kvm_pmu_counter_deferred(attr))
+		armv8pmu_disable_counter(mask);
 }
 
-static inline int armv8pmu_enable_intens(int idx)
+static inline void armv8pmu_enable_intens(u32 mask)
 {
-	u32 counter = ARMV8_IDX_TO_COUNTER(idx);
-	write_sysreg(BIT(counter), pmintenset_el1);
-	return idx;
+	write_sysreg(mask, pmintenset_el1);
 }
 
-static inline int armv8pmu_enable_event_irq(struct perf_event *event)
+static inline void armv8pmu_enable_event_irq(struct perf_event *event)
 {
-	return armv8pmu_enable_intens(event->hw.idx);
+	u32 counter = ARMV8_IDX_TO_COUNTER(event->hw.idx);
+	armv8pmu_enable_intens(BIT(counter));
 }
 
-static inline int armv8pmu_disable_intens(int idx)
+static inline void armv8pmu_disable_intens(u32 mask)
 {
-	u32 counter = ARMV8_IDX_TO_COUNTER(idx);
-	write_sysreg(BIT(counter), pmintenclr_el1);
+	write_sysreg(mask, pmintenclr_el1);
 	isb();
 	/* Clear the overflow flag in case an interrupt is pending. */
-	write_sysreg(BIT(counter), pmovsclr_el0);
+	write_sysreg(mask, pmovsclr_el0);
 	isb();
-
-	return idx;
 }
 
-static inline int armv8pmu_disable_event_irq(struct perf_event *event)
+static inline void armv8pmu_disable_event_irq(struct perf_event *event)
 {
-	return armv8pmu_disable_intens(event->hw.idx);
+	u32 counter = ARMV8_IDX_TO_COUNTER(event->hw.idx);
+	armv8pmu_disable_intens(BIT(counter));
 }
 
 static inline u32 armv8pmu_getreset_flags(void)
···
 
 static void armv8pmu_reset(void *info)
 {
-	struct arm_pmu *cpu_pmu = (struct arm_pmu *)info;
-	u32 idx, nb_cnt = cpu_pmu->num_events;
-
 	/* The counter and interrupt enable registers are unknown at reset. */
-	for (idx = ARMV8_IDX_CYCLE_COUNTER; idx < nb_cnt; ++idx) {
-		armv8pmu_disable_counter(idx);
-		armv8pmu_disable_intens(idx);
-	}
+	armv8pmu_disable_counter(U32_MAX);
+	armv8pmu_disable_intens(U32_MAX);
 
 	/* Clear the counters we flip at guest entry/exit */
 	kvm_clr_pmu_events(U32_MAX);