3 files changed, 28 insertions, 7 deletions

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index cea567483274..0a18d16cb58d 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -1671,25 +1671,32 @@ static const struct attribute_group *x86_pmu_attr_groups[] = {
         NULL,
 };
 
+static void x86_pmu_flush_branch_stack(void)
+{
+        if (x86_pmu.flush_branch_stack)
+                x86_pmu.flush_branch_stack();
+}
+
 static struct pmu pmu = {
-        .pmu_enable     = x86_pmu_enable,
-        .pmu_disable    = x86_pmu_disable,
+        .pmu_enable             = x86_pmu_enable,
+        .pmu_disable            = x86_pmu_disable,
 
         .attr_groups    = x86_pmu_attr_groups,
 
         .event_init     = x86_pmu_event_init,
 
-        .add            = x86_pmu_add,
-        .del            = x86_pmu_del,
-        .start          = x86_pmu_start,
-        .stop           = x86_pmu_stop,
-        .read           = x86_pmu_read,
+        .add                    = x86_pmu_add,
+        .del                    = x86_pmu_del,
+        .start                  = x86_pmu_start,
+        .stop                   = x86_pmu_stop,
+        .read                   = x86_pmu_read,
 
         .start_txn      = x86_pmu_start_txn,
         .cancel_txn     = x86_pmu_cancel_txn,
         .commit_txn     = x86_pmu_commit_txn,
 
         .event_idx      = x86_pmu_event_idx,
+        .flush_branch_stack     = x86_pmu_flush_branch_stack,
 };
 
 void perf_update_user_clock(struct perf_event_mmap_page *userpg, u64 now)
diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h
index f104c054dc5c..74387c12dc72 100644
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -324,6 +324,7 @@ struct x86_pmu {
         void            (*cpu_starting)(int cpu);
         void            (*cpu_dying)(int cpu);
         void            (*cpu_dead)(int cpu);
+        void            (*flush_branch_stack)(void);
 
         /*
          * Intel Arch Perfmon v2+
diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index 7cc1e2dcc4dd..6627089232a7 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1539,6 +1539,18 @@ static void intel_pmu_cpu_dying(int cpu)
         fini_debug_store_on_cpu(cpu);
 }
 
+static void intel_pmu_flush_branch_stack(void)
+{
+        /*
+         * Intel LBR does not tag entries with the
+         * PID of the current task, then we need to
+         * flush it on ctxsw
+         * For now, we simply reset it
+         */
+        if (x86_pmu.lbr_nr)
+                intel_pmu_lbr_reset();
+}
+
 static __initconst const struct x86_pmu intel_pmu = {
         .name                   = "Intel",
         .handle_irq             = intel_pmu_handle_irq,
@@ -1566,6 +1578,7 @@ static __initconst const struct x86_pmu intel_pmu = {
         .cpu_starting           = intel_pmu_cpu_starting,
         .cpu_dying              = intel_pmu_cpu_dying,
         .guest_get_msrs         = intel_guest_get_msrs,
+        .flush_branch_stack     = intel_pmu_flush_branch_stack,
 };
 
 static __init void intel_clovertown_quirk(void)