perf/x86/intel/uncore: Add infrastructure for free running counters

There are a number of free running counters introduced for uncore, which
provide highly valuable information to a wide array of customers.
However, the generic uncore code doesn't support them yet.

The free running counters will be specially handled based on their
unique attributes:

 - They are read-only. They cannot be enabled/disabled.

 - The event and the counter are always 1:1 mapped. It doesn't need to
   be assigned nor tracked by event_list.

 - They are always active. It doesn't need to check the availability.

 - They have different bit width.

Also, using inline helpers to replace the check for fixed counter and
free running counter.

Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: acme@kernel.org
Cc: eranian@google.com
Link: http://lkml.kernel.org/r/1525371913-10597-5-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 64 insertions, 4 deletions

diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
index 3b0f93eb3cc0..0a6f6973690b 100644
--- a/arch/x86/events/intel/uncore.c
+++ b/arch/x86/events/intel/uncore.c
@@ -203,7 +203,7 @@ static void uncore_assign_hw_event(struct intel_uncore_box *box,
         hwc->idx = idx;
         hwc->last_tag = ++box->tags[idx];
 
-        if (hwc->idx == UNCORE_PMC_IDX_FIXED) {
+        if (uncore_pmc_fixed(hwc->idx)) {
                 hwc->event_base = uncore_fixed_ctr(box);
                 hwc->config_base = uncore_fixed_ctl(box);
                 return;
@@ -218,7 +218,9 @@ void uncore_perf_event_update(struct intel_uncore_box *box, struct perf_event *e
         u64 prev_count, new_count, delta;
         int shift;
 
-        if (event->hw.idx == UNCORE_PMC_IDX_FIXED)
+        if (uncore_pmc_freerunning(event->hw.idx))
+                shift = 64 - uncore_freerunning_bits(box, event);
+        else if (uncore_pmc_fixed(event->hw.idx))
                 shift = 64 - uncore_fixed_ctr_bits(box);
         else
                 shift = 64 - uncore_perf_ctr_bits(box);
@@ -454,10 +456,25 @@ static void uncore_pmu_event_start(struct perf_event *event, int flags)
         struct intel_uncore_box *box = uncore_event_to_box(event);
         int idx = event->hw.idx;
 
-        if (WARN_ON_ONCE(!(event->hw.state & PERF_HES_STOPPED)))
+        if (WARN_ON_ONCE(idx == -1 || idx >= UNCORE_PMC_IDX_MAX))
                 return;
 
-        if (WARN_ON_ONCE(idx == -1 || idx >= UNCORE_PMC_IDX_MAX))
+        /*
+         * Free running counter is read-only and always active.
+         * Use the current counter value as start point.
+         * There is no overflow interrupt for free running counter.
+         * Use hrtimer to periodically poll the counter to avoid overflow.
+         */
+        if (uncore_pmc_freerunning(event->hw.idx)) {
+                list_add_tail(&event->active_entry, &box->active_list);
+                local64_set(&event->hw.prev_count,
+                            uncore_read_counter(box, event));
+                if (box->n_active++ == 0)
+                        uncore_pmu_start_hrtimer(box);
+                return;
+        }
+
+        if (WARN_ON_ONCE(!(event->hw.state & PERF_HES_STOPPED)))
                 return;
 
         event->hw.state = 0;
@@ -479,6 +496,15 @@ static void uncore_pmu_event_stop(struct perf_event *event, int flags)
         struct intel_uncore_box *box = uncore_event_to_box(event);
         struct hw_perf_event *hwc = &event->hw;
 
+        /* Cannot disable free running counter which is read-only */
+        if (uncore_pmc_freerunning(hwc->idx)) {
+                list_del(&event->active_entry);
+                if (--box->n_active == 0)
+                        uncore_pmu_cancel_hrtimer(box);
+                uncore_perf_event_update(box, event);
+                return;
+        }
+
         if (__test_and_clear_bit(hwc->idx, box->active_mask)) {
                 uncore_disable_event(box, event);
                 box->n_active--;
@@ -512,6 +538,17 @@ static int uncore_pmu_event_add(struct perf_event *event, int flags)
         if (!box)
                 return -ENODEV;
 
+        /*
+         * The free funning counter is assigned in event_init().
+         * The free running counter event and free running counter
+         * are 1:1 mapped. It doesn't need to be tracked in event_list.
+         */
+        if (uncore_pmc_freerunning(hwc->idx)) {
+                if (flags & PERF_EF_START)
+                        uncore_pmu_event_start(event, 0);
+                return 0;
+        }
+
         ret = n = uncore_collect_events(box, event, false);
         if (ret < 0)
                 return ret;
@@ -570,6 +607,14 @@ static void uncore_pmu_event_del(struct perf_event *event, int flags)
 
         uncore_pmu_event_stop(event, PERF_EF_UPDATE);
 
+        /*
+         * The event for free running counter is not tracked by event_list.
+         * It doesn't need to force event->hw.idx = -1 to reassign the counter.
+         * Because the event and the free running counter are 1:1 mapped.
+         */
+        if (uncore_pmc_freerunning(event->hw.idx))
+                return;
+
         for (i = 0; i < box->n_events; i++) {
                 if (event == box->event_list[i]) {
                         uncore_put_event_constraint(box, event);
@@ -603,6 +648,10 @@ static int uncore_validate_group(struct intel_uncore_pmu *pmu,
         struct intel_uncore_box *fake_box;
         int ret = -EINVAL, n;
 
+        /* The free running counter is always active. */
+        if (uncore_pmc_freerunning(event->hw.idx))
+                return 0;
+
         fake_box = uncore_alloc_box(pmu->type, NUMA_NO_NODE);
         if (!fake_box)
                 return -ENOMEM;
@@ -690,6 +739,17 @@ static int uncore_pmu_event_init(struct perf_event *event)
 
                 /* fixed counters have event field hardcoded to zero */
                 hwc->config = 0ULL;
+        } else if (is_freerunning_event(event)) {
+                if (!check_valid_freerunning_event(box, event))
+                        return -EINVAL;
+                event->hw.idx = UNCORE_PMC_IDX_FREERUNNING;
+                /*
+                 * The free running counter event and free running counter
+                 * are always 1:1 mapped.
+                 * The free running counter is always active.
+                 * Assign the free running counter here.
+                 */
+                event->hw.event_base = uncore_freerunning_counter(box, event);
         } else {
                 hwc->config = event->attr.config &
                               (pmu->type->event_mask | ((u64)pmu->type->event_mask_ext << 32));