From d9c2cb7bd89b32a9c7c26d6edc0f0c4c4df8e954 Mon Sep 17 00:00:00 2001
From: Cyrill Gorcunov <gorcunov@openvz.org>
Date: Thu, 3 Jun 2010 01:23:04 +0400
Subject: [PATCH] --- yaml --- r: 205246 b: refs/heads/master c:
 68aa00ac0a82e9a876c799bf6be7622b8f1c8517 h: refs/heads/master v: v3

---
 [refs]                                    |  2 +-
 trunk/arch/x86/kernel/cpu/perf_event.c    | 12 +++++++++++-
 trunk/arch/x86/kernel/cpu/perf_event_p4.c |  9 +++++++++
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/[refs] b/[refs]
index ed5eed025e72..a2877c19ff48 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 8d2cacbbb8deadfae78aa16e4e1ee619bdd7019e
+refs/heads/master: 68aa00ac0a82e9a876c799bf6be7622b8f1c8517
diff --git a/trunk/arch/x86/kernel/cpu/perf_event.c b/trunk/arch/x86/kernel/cpu/perf_event.c
index af04c6fa59cb..79e199843db6 100644
--- a/trunk/arch/x86/kernel/cpu/perf_event.c
+++ b/trunk/arch/x86/kernel/cpu/perf_event.c
@@ -220,6 +220,7 @@ struct x86_pmu {
 						 struct perf_event *event);
 	struct event_constraint *event_constraints;
 	void		(*quirks)(void);
+	int		perfctr_second_write;
 
 	int		(*cpu_prepare)(int cpu);
 	void		(*cpu_starting)(int cpu);
@@ -925,8 +926,17 @@ x86_perf_event_set_period(struct perf_event *event)
 	 */
 	atomic64_set(&hwc->prev_count, (u64)-left);
 
-	wrmsrl(hwc->event_base + idx,
+	wrmsrl(hwc->event_base + idx, (u64)(-left) & x86_pmu.cntval_mask);
+
+	/*
+	 * 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 + idx,
 			(u64)(-left) & x86_pmu.cntval_mask);
+	}
 
 	perf_event_update_userpage(event);
 
diff --git a/trunk/arch/x86/kernel/cpu/perf_event_p4.c b/trunk/arch/x86/kernel/cpu/perf_event_p4.c
index ae85d69644d1..9286e736a70a 100644
--- a/trunk/arch/x86/kernel/cpu/perf_event_p4.c
+++ b/trunk/arch/x86/kernel/cpu/perf_event_p4.c
@@ -829,6 +829,15 @@ static __initconst const struct x86_pmu p4_pmu = {
 	.max_period		= (1ULL << 39) - 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,
 };
 
 static __init int p4_pmu_init(void)