[PATCH V13 - RESEND 10/10] arm64/perf: Implement branch records save on PMU IRQ

From: Anshuman Khandual
Date: Tue Jul 11 2023 - 04:27:03 EST


This modifies armv8pmu_branch_read() to concatenate live entries along with
task context stored entries and then process the resultant buffer to create
perf branch entry array for perf_sample_data. It follows the same principle
like task sched out.

Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Tested-by: James Clark <james.clark@xxxxxxx>
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
---
drivers/perf/arm_brbe.c | 69 +++++++++++++++++++----------------------
1 file changed, 32 insertions(+), 37 deletions(-)

diff --git a/drivers/perf/arm_brbe.c b/drivers/perf/arm_brbe.c
index 2177632befa6..cb765aaf1b52 100644
--- a/drivers/perf/arm_brbe.c
+++ b/drivers/perf/arm_brbe.c
@@ -647,41 +647,44 @@ void armv8pmu_branch_reset(void)
isb();
}

-static bool capture_branch_entry(struct pmu_hw_events *cpuc,
- struct perf_event *event, int idx)
+static void brbe_regset_branch_entries(struct pmu_hw_events *cpuc, struct perf_event *event,
+ struct brbe_regset *regset, int idx)
{
struct perf_branch_entry *entry = &cpuc->branches->branch_entries[idx];
- u64 brbinf = get_brbinf_reg(idx);
-
- /*
- * There are no valid entries anymore on the buffer.
- * Abort the branch record processing to save some
- * cycles and also reduce the capture/process load
- * for the user space as well.
- */
- if (brbe_invalid(brbinf))
- return false;
+ u64 brbinf = regset[idx].brbinf;

perf_clear_branch_entry_bitfields(entry);
if (brbe_record_is_complete(brbinf)) {
- entry->from = get_brbsrc_reg(idx);
- entry->to = get_brbtgt_reg(idx);
+ entry->from = regset[idx].brbsrc;
+ entry->to = regset[idx].brbtgt;
} else if (brbe_record_is_source_only(brbinf)) {
- entry->from = get_brbsrc_reg(idx);
+ entry->from = regset[idx].brbsrc;
entry->to = 0;
} else if (brbe_record_is_target_only(brbinf)) {
entry->from = 0;
- entry->to = get_brbtgt_reg(idx);
+ entry->to = regset[idx].brbtgt;
}
capture_brbe_flags(entry, event, brbinf);
- return true;
+}
+
+static void process_branch_entries(struct pmu_hw_events *cpuc, struct perf_event *event,
+ struct brbe_regset *regset, int nr_regset)
+{
+ int idx;
+
+ for (idx = 0; idx < nr_regset; idx++)
+ brbe_regset_branch_entries(cpuc, event, regset, idx);
+
+ cpuc->branches->branch_stack.nr = nr_regset;
+ cpuc->branches->branch_stack.hw_idx = -1ULL;
}

void armv8pmu_branch_read(struct pmu_hw_events *cpuc, struct perf_event *event)
{
- int nr_hw_entries = brbe_get_numrec(cpuc->percpu_pmu->reg_brbidr);
+ struct arm64_perf_task_context *task_ctx = event->pmu_ctx->task_ctx_data;
+ struct brbe_regset live[BRBE_MAX_ENTRIES];
+ int nr_live, nr_store, nr_hw_entries;
u64 brbfcr, brbcr;
- int idx = 0;

brbcr = read_sysreg_s(SYS_BRBCR_EL1);
brbfcr = read_sysreg_s(SYS_BRBFCR_EL1);
@@ -693,25 +696,17 @@ void armv8pmu_branch_read(struct pmu_hw_events *cpuc, struct perf_event *event)
write_sysreg_s(brbfcr | BRBFCR_EL1_PAUSED, SYS_BRBFCR_EL1);
isb();

- /* Loop through bank 0 */
- select_brbe_bank(BRBE_BANK_IDX_0);
- while (idx < nr_hw_entries && idx <= BRBE_BANK0_IDX_MAX) {
- if (!capture_branch_entry(cpuc, event, idx))
- goto skip_bank_1;
- idx++;
- }
-
- /* Loop through bank 1 */
- select_brbe_bank(BRBE_BANK_IDX_1);
- while (idx < nr_hw_entries && idx <= BRBE_BANK1_IDX_MAX) {
- if (!capture_branch_entry(cpuc, event, idx))
- break;
- idx++;
+ nr_hw_entries = brbe_get_numrec(cpuc->percpu_pmu->reg_brbidr);
+ nr_live = capture_brbe_regset(live, nr_hw_entries);
+ if (event->ctx->task) {
+ nr_store = task_ctx->nr_brbe_records;
+ nr_store = stitch_stored_live_entries(task_ctx->store, live, nr_store,
+ nr_live, nr_hw_entries);
+ process_branch_entries(cpuc, event, task_ctx->store, nr_store);
+ task_ctx->nr_brbe_records = 0;
+ } else {
+ process_branch_entries(cpuc, event, live, nr_live);
}
-
-skip_bank_1:
- cpuc->branches->branch_stack.nr = idx;
- cpuc->branches->branch_stack.hw_idx = -1ULL;
process_branch_aborts(cpuc);

/* Unpause the buffer */
--
2.25.1