perf/x86: Support sysfs files depending on SMT status

Add a way to show different sysfs events attributes depending on
HyperThreading is on or off. This is difficult to determine
early at boot, so we just do it dynamically when the sysfs
attribute is read.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: acme@kernel.org
Cc: jolsa@kernel.org
Link: http://lkml.kernel.org/r/1463703002-19686-3-git-send-email-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

3 files changed, 40 insertions, 0 deletions

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 33787ee817f0..929655db5084 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -1622,6 +1622,29 @@ ssize_t events_sysfs_show(struct device *dev, struct device_attribute *attr, cha
 }
 EXPORT_SYMBOL_GPL(events_sysfs_show);
 
+ssize_t events_ht_sysfs_show(struct device *dev, struct device_attribute *attr,
+                          char *page)
+{
+        struct perf_pmu_events_ht_attr *pmu_attr =
+                container_of(attr, struct perf_pmu_events_ht_attr, attr);
+
+        /*
+         * Report conditional events depending on Hyper-Threading.
+         *
+         * This is overly conservative as usually the HT special
+         * handling is not needed if the other CPU thread is idle.
+         *
+         * Note this does not (and cannot) handle the case when thread
+         * siblings are invisible, for example with virtualization
+         * if they are owned by some other guest.  The user tool
+         * has to re-read when a thread sibling gets onlined later.
+         */
+        return sprintf(page, "%s",
+                        topology_max_smt_threads() > 1 ?
+                        pmu_attr->event_str_ht :
+                        pmu_attr->event_str_noht);
+}
+
 EVENT_ATTR(cpu-cycles,                  CPU_CYCLES              );
 EVENT_ATTR(instructions,                INSTRUCTIONS            );
 EVENT_ATTR(cache-references,            CACHE_REFERENCES        );
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 8bd764df815d..e2d7285a2dac 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -668,6 +668,14 @@ static struct perf_pmu_events_attr event_attr_##v = {			\
         .event_str      = str,                                          \
 };
 
+#define EVENT_ATTR_STR_HT(_name, v, noht, ht)                           \
+static struct perf_pmu_events_ht_attr event_attr_##v = {                \
+        .attr           = __ATTR(_name, 0444, events_ht_sysfs_show, NULL),\
+        .id             = 0,                                            \
+        .event_str_noht = noht,                                         \
+        .event_str_ht   = ht,                                           \
+}
+
 extern struct x86_pmu x86_pmu __read_mostly;
 
 static inline bool x86_pmu_has_lbr_callstack(void)
@@ -803,6 +811,8 @@ struct attribute **merge_attr(struct attribute **a, struct attribute **b);
 
 ssize_t events_sysfs_show(struct device *dev, struct device_attribute *attr,
                           char *page);
+ssize_t events_ht_sysfs_show(struct device *dev, struct device_attribute *attr,
+                          char *page);
 
 #ifdef CONFIG_CPU_SUP_AMD
 
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 92e9ce737432..a7593d653b40 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1334,6 +1334,13 @@ struct perf_pmu_events_attr {
         const char *event_str;
 };
 
+struct perf_pmu_events_ht_attr {
+        struct device_attribute                 attr;
+        u64                                     id;
+        const char                              *event_str_ht;
+        const char                              *event_str_noht;
+};
+
 ssize_t perf_event_sysfs_show(struct device *dev, struct device_attribute *attr,
                               char *page);