linux-kernel - [PATCH v2 7/9] perf/x86/p4: Remove perfctr_second

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Date:   Mon, 29 Aug 2022 12:10:06 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org, kan.liang@...ux.intel.com, eranian@...gle.com,
        ravi.bangoria@....com
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        acme@...nel.org, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
        namhyung@...nel.org
Subject: [PATCH v2 7/9] perf/x86/p4: Remove perfctr_second_write quirk

Now that we have a x86_pmu::set_period() method, use it to remove the
perfctr_second_write quirk from the generic code.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/events/core.c       |   12 +-----------
 arch/x86/events/intel/p4.c   |   37 +++++++++++++++++++++++++++----------
 arch/x86/events/perf_event.h |    2 +-
 3 files changed, 29 insertions(+), 22 deletions(-)

--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -1356,7 +1356,7 @@ static void x86_pmu_enable(struct pmu *p
 	static_call(x86_pmu_enable_all)(added);
 }
 
-static DEFINE_PER_CPU(u64 [X86_PMC_IDX_MAX], pmc_prev_left);
+DEFINE_PER_CPU(u64 [X86_PMC_IDX_MAX], pmc_prev_left);
 
 /*
  * Set the next IRQ period, based on the hwc->period_left value.
@@ -1416,16 +1416,6 @@ int x86_perf_event_set_period(struct per
 	if (is_counter_pair(hwc))
 		wrmsrl(x86_pmu_event_addr(idx + 1), 0xffff);
 
-	/*
-	 * Due to erratum on certan cpu we need
-	 * a second write to be sure the register
-	 * is updated properly
-	 */
-	if (x86_pmu.perfctr_second_write) {
-		wrmsrl(hwc->event_base,
-			(u64)(-left) & x86_pmu.cntval_mask);
-	}
-
 	perf_event_update_userpage(event);
 
 	return ret;
--- a/arch/x86/events/intel/p4.c
+++ b/arch/x86/events/intel/p4.c
@@ -1006,6 +1006,29 @@ static void p4_pmu_enable_all(int added)
 	}
 }
 
+static int p4_pmu_set_period(struct perf_event *event)
+{
+	struct hw_perf_event *hwc = &event->hw;
+	s64 left = this_cpu_read(pmc_prev_left[hwc->idx]);
+	int ret;
+
+	ret = x86_perf_event_set_period(event);
+
+	if (hwc->event_base) {
+		/*
+		 * This handles erratum N15 in intel doc 249199-029,
+		 * the counter may not be updated correctly on write
+		 * so we need a second write operation to do the trick
+		 * (the official workaround didn't work)
+		 *
+		 * the former idea is taken from OProfile code
+		 */
+		wrmsrl(hwc->event_base, (u64)(-left) & x86_pmu.cntval_mask);
+	}
+
+	return ret;
+}
+
 static int p4_pmu_handle_irq(struct pt_regs *regs)
 {
 	struct perf_sample_data data;
@@ -1044,7 +1067,7 @@ static int p4_pmu_handle_irq(struct pt_r
 		/* event overflow for sure */
 		perf_sample_data_init(&data, 0, hwc->last_period);
 
-		if (!x86_perf_event_set_period(event))
+		if (!static_call(x86_pmu_set_period)(event))
 			continue;
 
 
@@ -1316,6 +1339,9 @@ static __initconst const struct x86_pmu
 	.enable_all		= p4_pmu_enable_all,
 	.enable			= p4_pmu_enable_event,
 	.disable		= p4_pmu_disable_event,
+
+	.set_period		= p4_pmu_set_period,
+
 	.eventsel		= MSR_P4_BPU_CCCR0,
 	.perfctr		= MSR_P4_BPU_PERFCTR0,
 	.event_map		= p4_pmu_event_map,
@@ -1334,15 +1360,6 @@ static __initconst const struct x86_pmu
 	.max_period		= (1ULL << (ARCH_P4_CNTRVAL_BITS - 1)) - 1,
 	.hw_config		= p4_hw_config,
 	.schedule_events	= p4_pmu_schedule_events,
-	/*
-	 * This handles erratum N15 in intel doc 249199-029,
-	 * the counter may not be updated correctly on write
-	 * so we need a second write operation to do the trick
-	 * (the official workaround didn't work)
-	 *
-	 * the former idea is taken from OProfile code
-	 */
-	.perfctr_second_write	= 1,
 
 	.format_attrs		= intel_p4_formats_attr,
 };
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -772,7 +772,6 @@ struct x86_pmu {
 
 	struct event_constraint *event_constraints;
 	struct x86_pmu_quirk *quirks;
-	int		perfctr_second_write;
 	void		(*limit_period)(struct perf_event *event, s64 *l);
 
 	/* PMI handler bits */
@@ -1049,6 +1048,7 @@ static inline bool x86_pmu_has_lbr_calls
 }
 
 DECLARE_PER_CPU(struct cpu_hw_events, cpu_hw_events);
+DECLARE_PER_CPU(u64 [X86_PMC_IDX_MAX], pmc_prev_left);
 
 int x86_perf_event_set_period(struct perf_event *event);