perf/x86/intel/pt: Bypass PT vs. LBR exclusivity if the core supports it

Not all cores prevent using Intel PT and LBRs simultaneously, although
most of them still do as of today. This patch adds an opt-in flag for
such cores to disable mutual exclusivity between PT and LBR; also flip
it on for Goldmont.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.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: vince@deater.net
Link: http://lkml.kernel.org/r/1461857746-31346-4-git-send-email-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

3 files changed, 8 insertions, 0 deletions

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 41d93d0e972b..5e5e76a52f58 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -360,6 +360,9 @@ int x86_add_exclusive(unsigned int what)
 {
         int i;
 
+        if (x86_pmu.lbr_pt_coexist)
+                return 0;
+
         if (!atomic_inc_not_zero(&x86_pmu.lbr_exclusive[what])) {
                 mutex_lock(&pmc_reserve_mutex);
                 for (i = 0; i < ARRAY_SIZE(x86_pmu.lbr_exclusive); i++) {
@@ -380,6 +383,9 @@ fail_unlock:
 
 void x86_del_exclusive(unsigned int what)
 {
+        if (x86_pmu.lbr_pt_coexist)
+                return;
+
         atomic_dec(&x86_pmu.lbr_exclusive[what]);
         atomic_dec(&active_events);
 }
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 90ba3ae3074e..cd319400dc10 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3609,6 +3609,7 @@ __init int intel_pmu_init(void)
                  */
                 x86_pmu.pebs_aliases = NULL;
                 x86_pmu.pebs_prec_dist = true;
+                x86_pmu.lbr_pt_coexist = true;
                 x86_pmu.flags |= PMU_FL_HAS_RSP_1;
                 pr_cont("Goldmont events, ");
                 break;
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 7d62a02f49a4..8bd764df815d 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -601,6 +601,7 @@ struct x86_pmu {
         u64             lbr_sel_mask;              /* LBR_SELECT valid bits */
         const int       *lbr_sel_map;              /* lbr_select mappings */
         bool            lbr_double_abort;          /* duplicated lbr aborts */
+        bool            lbr_pt_coexist;            /* LBR may coexist with PT */
 
         /*
          * Intel PT/LBR/BTS are exclusive