[PATCH v2 1/9] arm64: perf: avoid PMXEV* indirection

[Julien Thierry <julien.thierry@arm.com>]

From: Mark Rutland <mark.rutland@arm.com>

Currently we access the counter registers and their respective type
registers indirectly. This requires us to write to PMSELR, issue an ISB,
then access the relevant PMXEV* registers.

This is unfortunate, because:

* Under virtualization, accessing one registers requires two traps to
  the hypervisor, even though we could access the register directly with
  a single trap.

* We have to issue an ISB which we could otherwise avoid the cost of.

* When we use NMIs, the NMI handler will have to save/restore the select
  register in case the code it preempted was attempting to access a
  counter or its type register.

We can avoid these issues by directly accessing the relevant registers.
This patch adds helpers to do so.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
[Julien T.: Don't inline read/write functions to avoid big code-size
	increase, remove unused read_pmevtypern function.]
Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
---
 arch/arm64/kernel/perf_event.c | 87 +++++++++++++++++++++++++++++++++++-------
 1 file changed, 74 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index 4addb38..63d45e2 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -379,6 +379,77 @@ static inline bool armv8pmu_event_is_chained(struct perf_event *event)
 #define	ARMV8_IDX_TO_COUNTER(x)	\
 	(((x) - ARMV8_IDX_COUNTER0) & ARMV8_PMU_COUNTER_MASK)

+/*
+ * This code is really good
+ */
+
+#define PMEVN_CASE(__n, case_macro) \
+	case __n: case_macro(__n); break;
+
+#define PMEVN_SWITCH(__x, case_macro)				\
+	do {							\
+		switch (__x) {					\
+		PMEVN_CASE(0,  case_macro);			\
+		PMEVN_CASE(1,  case_macro);			\
+		PMEVN_CASE(2,  case_macro);			\
+		PMEVN_CASE(3,  case_macro);			\
+		PMEVN_CASE(4,  case_macro);			\
+		PMEVN_CASE(5,  case_macro);			\
+		PMEVN_CASE(6,  case_macro);			\
+		PMEVN_CASE(7,  case_macro);			\
+		PMEVN_CASE(8,  case_macro);			\
+		PMEVN_CASE(9,  case_macro);			\
+		PMEVN_CASE(10, case_macro);			\
+		PMEVN_CASE(11, case_macro);			\
+		PMEVN_CASE(12, case_macro);			\
+		PMEVN_CASE(13, case_macro);			\
+		PMEVN_CASE(14, case_macro);			\
+		PMEVN_CASE(15, case_macro);			\
+		PMEVN_CASE(16, case_macro);			\
+		PMEVN_CASE(17, case_macro);			\
+		PMEVN_CASE(18, case_macro);			\
+		PMEVN_CASE(19, case_macro);			\
+		PMEVN_CASE(21, case_macro);			\
+		PMEVN_CASE(22, case_macro);			\
+		PMEVN_CASE(23, case_macro);			\
+		PMEVN_CASE(24, case_macro);			\
+		PMEVN_CASE(25, case_macro);			\
+		PMEVN_CASE(26, case_macro);			\
+		PMEVN_CASE(27, case_macro);			\
+		PMEVN_CASE(28, case_macro);			\
+		PMEVN_CASE(29, case_macro);			\
+		PMEVN_CASE(30, case_macro);			\
+		default: WARN(1, "Inavlid PMEV* index");	\
+		}						\
+	} while (0)
+
+#define RETURN_READ_PMEVCNTRN(n) \
+	return read_sysreg(pmevcntr##n##_el0);
+static unsigned long read_pmevcntrn(int n)
+{
+	PMEVN_SWITCH(n, RETURN_READ_PMEVCNTRN);
+	return 0;
+}
+#undef RETURN_READ_PMEVCNTRN
+
+#define WRITE_PMEVCNTRN(n) \
+	write_sysreg(val, pmevcntr##n##_el0);
+static void write_pmevcntrn(int n, unsigned long val)
+{
+	PMEVN_SWITCH(n, WRITE_PMEVCNTRN);
+}
+#undef WRITE_PMEVCNTRN
+
+#define WRITE_PMEVTYPERN(n) \
+	write_sysreg(val, pmevtyper##n##_el0);
+static void write_pmevtypern(int n, unsigned long val)
+{
+	PMEVN_SWITCH(n, WRITE_PMEVTYPERN);
+}
+#undef WRITE_PMEVTYPERN
+
+#undef GENERATE_PMEVN_SWITCH
+
 static inline u32 armv8pmu_pmcr_read(void)
 {
 	return read_sysreg(pmcr_el0);
@@ -407,17 +478,9 @@ static inline int armv8pmu_counter_has_overflowed(u32 pmnc, int idx)
 	return pmnc & BIT(ARMV8_IDX_TO_COUNTER(idx));
 }

-static inline void armv8pmu_select_counter(int idx)
-{
-	u32 counter = ARMV8_IDX_TO_COUNTER(idx);
-	write_sysreg(counter, pmselr_el0);
-	isb();
-}
-
 static inline u32 armv8pmu_read_evcntr(int idx)
 {
-	armv8pmu_select_counter(idx);
-	return read_sysreg(pmxevcntr_el0);
+	return read_pmevcntrn(idx);
 }

 static inline u64 armv8pmu_read_hw_counter(struct perf_event *event)
@@ -451,8 +514,7 @@ static inline u64 armv8pmu_read_counter(struct perf_event *event)

 static inline void armv8pmu_write_evcntr(int idx, u32 value)
 {
-	armv8pmu_select_counter(idx);
-	write_sysreg(value, pmxevcntr_el0);
+	write_pmevcntrn(idx, value);
 }

 static inline void armv8pmu_write_hw_counter(struct perf_event *event,
@@ -493,9 +555,8 @@ static inline void armv8pmu_write_counter(struct perf_event *event, u64 value)

 static inline void armv8pmu_write_evtype(int idx, u32 val)
 {
-	armv8pmu_select_counter(idx);
 	val &= ARMV8_PMU_EVTYPE_MASK;
-	write_sysreg(val, pmxevtyper_el0);
+	write_pmevtypern(idx, val);
 }

 static inline void armv8pmu_write_event_type(struct perf_event *event)
--
1.9.1

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