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Subject[tip:perf/hw-branch-sampling] perf/x86: Implement PERF_SAMPLE_BRANCH for Intel CPUs
Commit-ID:  60ce0fbd072695866cb27b729690ab59dce705a5
Gitweb: http://git.kernel.org/tip/60ce0fbd072695866cb27b729690ab59dce705a5
Author: Stephane Eranian <eranian@google.com>
AuthorDate: Thu, 9 Feb 2012 23:20:57 +0100
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 5 Mar 2012 14:55:41 +0100

perf/x86: Implement PERF_SAMPLE_BRANCH for Intel CPUs

This patch implements PERF_SAMPLE_BRANCH support for Intel
x86processors. It connects PERF_SAMPLE_BRANCH to the actual LBR.

The patch adds the hooks in the PMU irq handler to save the LBR
on counter overflow for both regular and PEBS modes.

Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1328826068-11713-8-git-send-email-eranian@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
arch/x86/kernel/cpu/perf_event.h | 2 +
arch/x86/kernel/cpu/perf_event_intel.c | 35 +++++++++++
arch/x86/kernel/cpu/perf_event_intel_ds.c | 10 +--
arch/x86/kernel/cpu/perf_event_intel_lbr.c | 86 +++++++++++++++++++++++++++-
4 files changed, 125 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h
index 4e94897..ef7419c 100644
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -541,6 +541,8 @@ void intel_pmu_lbr_init_atom(void);

void intel_pmu_lbr_init_snb(void);

+int intel_pmu_setup_lbr_filter(struct perf_event *event);
+
int p4_pmu_init(void);

int p6_pmu_init(void);
diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index b0db016..7cc1e2d 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -727,6 +727,19 @@ static __initconst const u64 atom_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)
+ return true;
+
+ return false;
+}
+
static void intel_pmu_disable_all(void)
{
struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
@@ -881,6 +894,13 @@ static void intel_pmu_disable_event(struct perf_event *event)
cpuc->intel_ctrl_guest_mask &= ~(1ull << hwc->idx);
cpuc->intel_ctrl_host_mask &= ~(1ull << hwc->idx);

+ /*
+ * must disable before any actual event
+ * because any event may be combined with LBR
+ */
+ if (intel_pmu_needs_lbr_smpl(event))
+ intel_pmu_lbr_disable(event);
+
if (unlikely(hwc->config_base == MSR_ARCH_PERFMON_FIXED_CTR_CTRL)) {
intel_pmu_disable_fixed(hwc);
return;
@@ -935,6 +955,12 @@ static void intel_pmu_enable_event(struct perf_event *event)
intel_pmu_enable_bts(hwc->config);
return;
}
+ /*
+ * must enabled before any actual event
+ * because any event may be combined with LBR
+ */
+ if (intel_pmu_needs_lbr_smpl(event))
+ intel_pmu_lbr_enable(event);

if (event->attr.exclude_host)
cpuc->intel_ctrl_guest_mask |= (1ull << hwc->idx);
@@ -1057,6 +1083,9 @@ again:

data.period = event->hw.last_period;

+ if (has_branch_stack(event))
+ data.br_stack = &cpuc->lbr_stack;
+
if (perf_event_overflow(event, &data, regs))
x86_pmu_stop(event, 0);
}
@@ -1305,6 +1334,12 @@ static int intel_pmu_hw_config(struct perf_event *event)
event->hw.config = alt_config;
}

+ if (intel_pmu_needs_lbr_smpl(event)) {
+ ret = intel_pmu_setup_lbr_filter(event);
+ if (ret)
+ return ret;
+ }
+
if (event->attr.type != PERF_TYPE_RAW)
return 0;

diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
index d6bd49f..ee7e3c8 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
@@ -439,9 +439,6 @@ void intel_pmu_pebs_enable(struct perf_event *event)
hwc->config &= ~ARCH_PERFMON_EVENTSEL_INT;

cpuc->pebs_enabled |= 1ULL << hwc->idx;
-
- if (x86_pmu.intel_cap.pebs_trap && event->attr.precise_ip > 1)
- intel_pmu_lbr_enable(event);
}

void intel_pmu_pebs_disable(struct perf_event *event)
@@ -454,9 +451,6 @@ void intel_pmu_pebs_disable(struct perf_event *event)
wrmsrl(MSR_IA32_PEBS_ENABLE, cpuc->pebs_enabled);

hwc->config |= ARCH_PERFMON_EVENTSEL_INT;
-
- if (x86_pmu.intel_cap.pebs_trap && event->attr.precise_ip > 1)
- intel_pmu_lbr_disable(event);
}

void intel_pmu_pebs_enable_all(void)
@@ -572,6 +566,7 @@ static void __intel_pmu_pebs_event(struct perf_event *event,
* both formats and we don't use the other fields in this
* routine.
*/
+ struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
struct pebs_record_core *pebs = __pebs;
struct perf_sample_data data;
struct pt_regs regs;
@@ -602,6 +597,9 @@ static void __intel_pmu_pebs_event(struct perf_event *event,
else
regs.flags &= ~PERF_EFLAGS_EXACT;

+ if (has_branch_stack(event))
+ data.br_stack = &cpuc->lbr_stack;
+
if (perf_event_overflow(event, &data, &regs))
x86_pmu_stop(event, 0);
}
diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
index 07f0ff8..d0fb864 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
@@ -56,6 +56,10 @@ enum {

#define LBR_FROM_FLAG_MISPRED (1ULL << 63)

+#define for_each_branch_sample_type(x) \
+ for ((x) = PERF_SAMPLE_BRANCH_USER; \
+ (x) < PERF_SAMPLE_BRANCH_MAX; (x) <<= 1)
+
/*
* We only support LBR implementations that have FREEZE_LBRS_ON_PMI
* otherwise it becomes near impossible to get a reliable stack.
@@ -64,6 +68,10 @@ enum {
static void __intel_pmu_lbr_enable(void)
{
u64 debugctl;
+ struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
+
+ if (cpuc->lbr_sel)
+ wrmsrl(MSR_LBR_SELECT, cpuc->lbr_sel->config);

rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
debugctl |= (DEBUGCTLMSR_LBR | DEBUGCTLMSR_FREEZE_LBRS_ON_PMI);
@@ -119,7 +127,6 @@ void intel_pmu_lbr_enable(struct perf_event *event)
* Reset the LBR stack if we changed task context to
* avoid data leaks.
*/
-
if (event->ctx->task && cpuc->lbr_context != event->ctx) {
intel_pmu_lbr_reset();
cpuc->lbr_context = event->ctx;
@@ -138,8 +145,11 @@ void intel_pmu_lbr_disable(struct perf_event *event)
cpuc->lbr_users--;
WARN_ON_ONCE(cpuc->lbr_users < 0);

- if (cpuc->enabled && !cpuc->lbr_users)
+ if (cpuc->enabled && !cpuc->lbr_users) {
__intel_pmu_lbr_disable();
+ /* avoid stale pointer */
+ cpuc->lbr_context = NULL;
+ }
}

void intel_pmu_lbr_enable_all(void)
@@ -158,6 +168,9 @@ void intel_pmu_lbr_disable_all(void)
__intel_pmu_lbr_disable();
}

+/*
+ * TOS = most recently recorded branch
+ */
static inline u64 intel_pmu_lbr_tos(void)
{
u64 tos;
@@ -242,6 +255,75 @@ void intel_pmu_lbr_read(void)
}

/*
+ * setup the HW LBR filter
+ * Used only when available, may not be enough to disambiguate
+ * all branches, may need the help of the SW filter
+ */
+static int intel_pmu_setup_hw_lbr_filter(struct perf_event *event)
+{
+ struct hw_perf_event_extra *reg;
+ u64 br_type = event->attr.branch_sample_type;
+ u64 mask = 0, m;
+ u64 v;
+
+ for_each_branch_sample_type(m) {
+ if (!(br_type & m))
+ continue;
+
+ v = x86_pmu.lbr_sel_map[m];
+ if (v == LBR_NOT_SUPP)
+ return -EOPNOTSUPP;
+ mask |= v;
+
+ if (m == PERF_SAMPLE_BRANCH_ANY)
+ break;
+ }
+ reg = &event->hw.branch_reg;
+ reg->idx = EXTRA_REG_LBR;
+
+ /* LBR_SELECT operates in suppress mode so invert mask */
+ reg->config = ~mask & x86_pmu.lbr_sel_mask;
+
+ return 0;
+}
+
+/*
+ * all the bits supported on some flavor of x86LBR
+ * we ignore BRANCH_HV because it is not supported
+ */
+#define PERF_SAMPLE_BRANCH_X86_ALL \
+ (PERF_SAMPLE_BRANCH_ANY |\
+ PERF_SAMPLE_BRANCH_USER |\
+ PERF_SAMPLE_BRANCH_KERNEL)
+
+int intel_pmu_setup_lbr_filter(struct perf_event *event)
+{
+ u64 br_type = event->attr.branch_sample_type;
+
+ /*
+ * no LBR on this PMU
+ */
+ if (!x86_pmu.lbr_nr)
+ return -EOPNOTSUPP;
+
+ /*
+ * if no LBR HW filter, users can only
+ * capture all branches
+ */
+ if (!x86_pmu.lbr_sel_map) {
+ if (br_type != PERF_SAMPLE_BRANCH_X86_ALL)
+ return -EOPNOTSUPP;
+ return 0;
+ }
+ /*
+ * we ignore branch priv levels we do not
+ * know about: BRANCH_HV
+ */
+
+ return intel_pmu_setup_hw_lbr_filter(event);
+}
+
+/*
* Map interface branch filters onto LBR filters
*/
static const int nhm_lbr_sel_map[PERF_SAMPLE_BRANCH_MAX] = {

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