perf/x86: Mark Intel PT and LBR/BTS as 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@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kaixu Xia <kaixu.xia@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Robert Richter <rric@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: acme@infradead.org
Cc: adrian.hunter@intel.com
Cc: kan.liang@intel.com
Cc: markus.t.metzger@intel.com
Cc: mathieu.poirier@linaro.org
Link: http://lkml.kernel.org/r/1421237903-181015-12-git-send-email-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 0420ebc..549d01d 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -263,6 +263,14 @@
}
}
+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;
@@ -302,6 +310,35 @@
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;
@@ -346,6 +383,12 @@
/* 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 87e5081..4749966 100644
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -408,6 +408,12 @@
#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
*/
@@ -506,6 +512,11 @@
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;
@@ -603,6 +614,12 @@
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);
@@ -689,6 +706,29 @@
#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 fc6dbc4..b7b3ff2 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1942,6 +1942,17 @@
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)