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Date: Fri, 14 Nov 2014 15:43:44 +0200
From: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
Robert Richter <rric@...nel.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Mike Galbraith <efault@....de>,
Paul Mackerras <paulus@...ba.org>,
Stephane Eranian <eranian@...gle.com>,
Andi Kleen <ak@...ux.intel.com>, kan.liang@...el.com,
adrian.hunter@...el.com, markus.t.metzger@...el.com,
mathieu.poirier@...aro.org, acme@...radead.org,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: [PATCH v8 11/14] x86: perf: Intel PT and LBR/BTS are mutually exclusive
Intel PT cannot be used at the same time as LBR or BTS and will cause a
general protection fault if they are used together. In order to avoid
fixing up GPs in the fast path, instead we disallow creating LBR/BTS
events when PT events are present and vice versa.
Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
---
arch/x86/kernel/cpu/perf_event.c | 43 ++++++++++++++++++++++++++++++++++
arch/x86/kernel/cpu/perf_event.h | 40 +++++++++++++++++++++++++++++++
arch/x86/kernel/cpu/perf_event_intel.c | 26 ++++++++++----------
3 files changed, 95 insertions(+), 14 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 143e5f5dc8..1cca1ac9b6 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -259,6 +259,14 @@ static void hw_perf_event_destroy(struct perf_event *event)
}
}
+void hw_perf_lbr_event_destroy(struct perf_event *event)
+{
+ hw_perf_event_destroy(event);
+
+ /* undo the lbr/bts event accounting */
+ x86_del_exclusive(x86_lbr_exclusive_lbr);
+}
+
static inline int x86_pmu_initialized(void)
{
return x86_pmu.handle_irq != NULL;
@@ -298,6 +306,35 @@ set_ext_hw_attr(struct hw_perf_event *hwc, struct perf_event *event)
return x86_pmu_extra_regs(val, event);
}
+/*
+ * Check if we can create event of a certain type (that no conflicting events
+ * are present).
+ */
+int x86_add_exclusive(unsigned int what)
+{
+ int ret = -EBUSY, i;
+
+ if (atomic_inc_not_zero(&x86_pmu.lbr_exclusive[what]))
+ return 0;
+
+ mutex_lock(&pmc_reserve_mutex);
+ for (i = 0; i < ARRAY_SIZE(x86_pmu.lbr_exclusive); i++)
+ if (i != what && atomic_read(&x86_pmu.lbr_exclusive[i]))
+ goto out;
+
+ atomic_inc(&x86_pmu.lbr_exclusive[what]);
+ ret = 0;
+
+out:
+ mutex_unlock(&pmc_reserve_mutex);
+ return ret;
+}
+
+void x86_del_exclusive(unsigned int what)
+{
+ atomic_dec(&x86_pmu.lbr_exclusive[what]);
+}
+
int x86_setup_perfctr(struct perf_event *event)
{
struct perf_event_attr *attr = &event->attr;
@@ -342,6 +379,12 @@ int x86_setup_perfctr(struct perf_event *event)
/* BTS is currently only allowed for user-mode. */
if (!attr->exclude_kernel)
return -EOPNOTSUPP;
+
+ /* disallow bts if conflicting events are present */
+ if (x86_add_exclusive(x86_lbr_exclusive_lbr))
+ return -EBUSY;
+
+ event->destroy = hw_perf_lbr_event_destroy;
}
hwc->config |= config;
diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h
index fc5eb390b3..620612d311 100644
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -402,6 +402,12 @@ union x86_pmu_config {
#define X86_CONFIG(args...) ((union x86_pmu_config){.bits = {args}}).value
+enum {
+ x86_lbr_exclusive_lbr,
+ x86_lbr_exclusive_pt,
+ x86_lbr_exclusive_max,
+};
+
/*
* struct x86_pmu - generic x86 pmu
*/
@@ -498,6 +504,11 @@ struct x86_pmu {
bool lbr_double_abort; /* duplicated lbr aborts */
/*
+ * Intel PT/LBR/BTS are exclusive
+ */
+ atomic_t lbr_exclusive[x86_lbr_exclusive_max];
+
+ /*
* Extra registers for events
*/
struct extra_reg *extra_regs;
@@ -582,6 +593,12 @@ static inline int x86_pmu_rdpmc_index(int index)
return x86_pmu.rdpmc_index ? x86_pmu.rdpmc_index(index) : index;
}
+int x86_add_exclusive(unsigned int what);
+
+void x86_del_exclusive(unsigned int what);
+
+void hw_perf_lbr_event_destroy(struct perf_event *event);
+
int x86_setup_perfctr(struct perf_event *event);
int x86_pmu_hw_config(struct perf_event *event);
@@ -668,6 +685,29 @@ static inline int amd_pmu_init(void)
#ifdef CONFIG_CPU_SUP_INTEL
+static inline bool intel_pmu_needs_lbr_smpl(struct perf_event *event)
+{
+ /* user explicitly requested branch sampling */
+ if (has_branch_stack(event))
+ return true;
+
+ /* implicit branch sampling to correct PEBS skid */
+ if (x86_pmu.intel_cap.pebs_trap && event->attr.precise_ip > 1 &&
+ x86_pmu.intel_cap.pebs_format < 2)
+ return true;
+
+ return false;
+}
+
+static inline bool intel_pmu_has_bts(struct perf_event *event)
+{
+ if (event->attr.config == PERF_COUNT_HW_BRANCH_INSTRUCTIONS &&
+ !event->attr.freq && event->hw.sample_period == 1)
+ return true;
+
+ return false;
+}
+
int intel_pmu_save_and_restart(struct perf_event *event);
struct event_constraint *
diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index 944bf019b7..c64e97a1cb 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1029,20 +1029,6 @@ static __initconst const u64 slm_hw_cache_event_ids
},
};
-static inline bool intel_pmu_needs_lbr_smpl(struct perf_event *event)
-{
- /* user explicitly requested branch sampling */
- if (has_branch_stack(event))
- return true;
-
- /* implicit branch sampling to correct PEBS skid */
- if (x86_pmu.intel_cap.pebs_trap && event->attr.precise_ip > 1 &&
- x86_pmu.intel_cap.pebs_format < 2)
- return true;
-
- return false;
-}
-
static void intel_pmu_disable_all(void)
{
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
@@ -1751,6 +1737,18 @@ static int intel_pmu_hw_config(struct perf_event *event)
ret = intel_pmu_setup_lbr_filter(event);
if (ret)
return ret;
+
+ /*
+ * bts is set up earlier in this path, so don't account
+ * twice
+ */
+ if (!intel_pmu_has_bts(event)) {
+ /* disallow lbr if conflicting events are present */
+ if (x86_add_exclusive(x86_lbr_exclusive_lbr))
+ return -EBUSY;
+
+ event->destroy = hw_perf_lbr_event_destroy;
+ }
}
if (event->attr.type != PERF_TYPE_RAW)
--
2.1.1
--
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