perf: arm_pmuv3: Add support for Armv9.4 PMU instruction counter

Armv9.4/8.9 PMU adds optional support for a fixed instruction counter
similar to the fixed cycle counter. Support for the feature is indicated
in the ID_AA64DFR1_EL1 register PMICNTR field. The counter is not
accessible in AArch32.

Existing userspace using direct counter access won't know how to handle
the fixed instruction counter, so we have to avoid using the counter
when user access is requested.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Tested-by: James Clark <james.clark@linaro.org>
Link: https://lore.kernel.org/r/20240731-arm-pmu-3-9-icntr-v3-7-280a8d7ff465@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

Author: robherring

arch/arm/include/asm/arm_pmuv3.h

@@ -127,6 +127,12 @@ static inline u32 read_pmuver(void)
 	return (dfr0 >> 24) & 0xf;
 }
 
+static inline bool pmuv3_has_icntr(void)
+{
+	/* FEAT_PMUv3_ICNTR not accessible for 32-bit */
+	return false;
+}
+
 static inline void write_pmcr(u32 val)
 {
 	write_sysreg(val, PMCR);
@@ -152,6 +158,13 @@ static inline u64 read_pmccntr(void)
 	return read_sysreg(PMCCNTR);
 }
 
+static inline void write_pmicntr(u64 val) {}
+
+static inline u64 read_pmicntr(void)
+{
+	return 0;
+}
+
 static inline void write_pmcntenset(u32 val)
 {
 	write_sysreg(val, PMCNTENSET);
@@ -177,6 +190,13 @@ static inline void write_pmccfiltr(u32 val)
 	write_sysreg(val, PMCCFILTR);
 }
 
+static inline void write_pmicfiltr(u64 val) {}
+
+static inline u64 read_pmicfiltr(void)
+{
+	return 0;
+}
+
 static inline void write_pmovsclr(u32 val)
 {
 	write_sysreg(val, PMOVSR);

arch/arm64/include/asm/arm_pmuv3.h

@@ -54,6 +54,14 @@ static inline u32 read_pmuver(void)
 			ID_AA64DFR0_EL1_PMUVer_SHIFT);
 }
 
+static inline bool pmuv3_has_icntr(void)
+{
+	u64 dfr1 = read_sysreg(id_aa64dfr1_el1);
+
+	return !!cpuid_feature_extract_unsigned_field(dfr1,
+			ID_AA64DFR1_EL1_PMICNTR_SHIFT);
+}
+
 static inline void write_pmcr(u64 val)
 {
 	write_sysreg(val, pmcr_el0);
@@ -79,6 +87,16 @@ static inline u64 read_pmccntr(void)
 	return read_sysreg(pmccntr_el0);
 }
 
+static inline void write_pmicntr(u64 val)
+{
+	write_sysreg_s(val, SYS_PMICNTR_EL0);
+}
+
+static inline u64 read_pmicntr(void)
+{
+	return read_sysreg_s(SYS_PMICNTR_EL0);
+}
+
 static inline void write_pmcntenset(u64 val)
 {
 	write_sysreg(val, pmcntenset_el0);
@@ -109,6 +127,16 @@ static inline u64 read_pmccfiltr(void)
 	return read_sysreg(pmccfiltr_el0);
 }
 
+static inline void write_pmicfiltr(u64 val)
+{
+	write_sysreg_s(val, SYS_PMICFILTR_EL0);
+}
+
+static inline u64 read_pmicfiltr(void)
+{
+	return read_sysreg_s(SYS_PMICFILTR_EL0);
+}
+
 static inline void write_pmovsclr(u64 val)
 {
 	write_sysreg(val, pmovsclr_el0);

arch/arm64/kvm/pmu.c

@@ -66,24 +66,28 @@ void kvm_clr_pmu_events(u64 clr)
 
 /*
  * Read a value direct from PMEVTYPER<idx> where idx is 0-30
- * or PMCCFILTR_EL0 where idx is ARMV8_PMU_CYCLE_IDX (31).
+ * or PMxCFILTR_EL0 where idx is 31-32.
  */
 static u64 kvm_vcpu_pmu_read_evtype_direct(int idx)
 {
 	if (idx == ARMV8_PMU_CYCLE_IDX)
 		return read_pmccfiltr();
+	else if (idx == ARMV8_PMU_INSTR_IDX)
+		return read_pmicfiltr();
 
 	return read_pmevtypern(idx);
 }
 
 /*
  * Write a value direct to PMEVTYPER<idx> where idx is 0-30
- * or PMCCFILTR_EL0 where idx is ARMV8_PMU_CYCLE_IDX (31).
+ * or PMxCFILTR_EL0 where idx is 31-32.
  */
 static void kvm_vcpu_pmu_write_evtype_direct(int idx, u32 val)
 {
 	if (idx == ARMV8_PMU_CYCLE_IDX)
 		write_pmccfiltr(val);
+	else if (idx == ARMV8_PMU_INSTR_IDX)
+		write_pmicfiltr(val);
 	else
 		write_pmevtypern(idx, val);
 }

arch/arm64/tools/sysreg

@@ -2029,6 +2029,31 @@ Sysreg	FAR_EL1	3	0	6	0	0
 Field	63:0	ADDR
 EndSysreg
 
+Sysreg	PMICNTR_EL0	3	3	9	4	0
+Field	63:0	ICNT
+EndSysreg
+
+Sysreg	PMICFILTR_EL0	3	3	9	6	0
+Res0	63:59
+Field	58	SYNC
+Field	57:56	VS
+Res0	55:32
+Field	31	P
+Field	30	U
+Field	29	NSK
+Field	28	NSU
+Field	27	NSH
+Field	26	M
+Res0	25
+Field	24	SH
+Field	23	T
+Field	22	RLK
+Field	21	RLU
+Field	20	RLH
+Res0	19:16
+Field	15:0	evtCount
+EndSysreg
+
 Sysreg	PMSCR_EL1	3	0	9	9	0
 Res0	63:8
 Field	7:6	PCT

drivers/perf/arm_pmuv3.c

@@ -571,6 +571,8 @@ static u64 armv8pmu_read_counter(struct perf_event *event)
 
 	if (idx == ARMV8_PMU_CYCLE_IDX)
 		value = read_pmccntr();
+	else if (idx == ARMV8_PMU_INSTR_IDX)
+		value = read_pmicntr();
 	else
 		value = armv8pmu_read_hw_counter(event);
 
@@ -604,6 +606,8 @@ static void armv8pmu_write_counter(struct perf_event *event, u64 value)
 
 	if (idx == ARMV8_PMU_CYCLE_IDX)
 		write_pmccntr(value);
+	else if (idx == ARMV8_PMU_INSTR_IDX)
+		write_pmicntr(value);
 	else
 		armv8pmu_write_hw_counter(event, value);
 }
@@ -641,6 +645,8 @@ static void armv8pmu_write_event_type(struct perf_event *event)
 	} else {
 		if (idx == ARMV8_PMU_CYCLE_IDX)
 			write_pmccfiltr(hwc->config_base);
+		else if (idx == ARMV8_PMU_INSTR_IDX)
+			write_pmicfiltr(hwc->config_base);
 		else
 			armv8pmu_write_evtype(idx, hwc->config_base);
 	}
@@ -769,6 +775,8 @@ static void armv8pmu_enable_user_access(struct arm_pmu *cpu_pmu)
 			    ARMPMU_MAX_HWEVENTS) {
 		if (i == ARMV8_PMU_CYCLE_IDX)
 			write_pmccntr(0);
+		else if (i == ARMV8_PMU_INSTR_IDX)
+			write_pmicntr(0);
 		else
 			armv8pmu_write_evcntr(i, 0);
 	}
@@ -936,6 +944,19 @@ static int armv8pmu_get_event_idx(struct pmu_hw_events *cpuc,
 				return -EAGAIN;
 	}
 
+	/*
+	 * Always prefer to place a instruction counter into the instruction counter,
+	 * but don't expose the instruction counter to userspace access as userspace
+	 * may not know how to handle it.
+	 */
+	if ((evtype == ARMV8_PMUV3_PERFCTR_INST_RETIRED) &&
+	    !armv8pmu_event_get_threshold(&event->attr) &&
+	    test_bit(ARMV8_PMU_INSTR_IDX, cpu_pmu->cntr_mask) &&
+	    !armv8pmu_event_want_user_access(event)) {
+		if (!test_and_set_bit(ARMV8_PMU_INSTR_IDX, cpuc->used_mask))
+			return ARMV8_PMU_INSTR_IDX;
+	}
+
 	/*
 	 * Otherwise use events counters
 	 */
@@ -1193,6 +1214,10 @@ static void __armv8pmu_probe_pmu(void *info)
 	/* Add the CPU cycles counter */
 	set_bit(ARMV8_PMU_CYCLE_IDX, cpu_pmu->cntr_mask);
 
+	/* Add the CPU instructions counter */
+	if (pmuv3_has_icntr())
+		set_bit(ARMV8_PMU_INSTR_IDX, cpu_pmu->cntr_mask);
+
 	pmceid[0] = pmceid_raw[0] = read_pmceid0();
 	pmceid[1] = pmceid_raw[1] = read_pmceid1();
 

include/linux/perf/arm_pmu.h

@@ -17,10 +17,14 @@
 #ifdef CONFIG_ARM_PMU
 
 /*
- * The ARMv7 CPU PMU supports up to 32 event counters.
+ * The Armv7 and Armv8.8 or less CPU PMU supports up to 32 event counters.
+ * The Armv8.9/9.4 CPU PMU supports up to 33 event counters.
  */
+#ifdef CONFIG_ARM
 #define ARMPMU_MAX_HWEVENTS		32
-
+#else
+#define ARMPMU_MAX_HWEVENTS		33
+#endif
 /*
  * ARM PMU hw_event flags
  */

include/linux/perf/arm_pmuv3.h

@@ -8,7 +8,7 @@
 
 #define ARMV8_PMU_MAX_GENERAL_COUNTERS	31
 #define ARMV8_PMU_CYCLE_IDX		31
-
+#define ARMV8_PMU_INSTR_IDX		32 /* Not accessible from AArch32 */
 
 /*
  * Common architectural and microarchitectural event numbers.
@@ -228,8 +228,10 @@
  */
 #define ARMV8_PMU_OVSR_P		GENMASK(30, 0)
 #define ARMV8_PMU_OVSR_C		BIT(31)
+#define ARMV8_PMU_OVSR_F		BIT_ULL(32) /* arm64 only */
 /* Mask for writable bits is both P and C fields */
-#define ARMV8_PMU_OVERFLOWED_MASK	(ARMV8_PMU_OVSR_P | ARMV8_PMU_OVSR_C)
+#define ARMV8_PMU_OVERFLOWED_MASK	(ARMV8_PMU_OVSR_P | ARMV8_PMU_OVSR_C | \
+					ARMV8_PMU_OVSR_F)
 
 /*
  * PMXEVTYPER: Event selection reg