trace: Properly initialize dynamic event states in hot-plugged vCPUs

Every time a vCPU is hot-plugged, it will "inherit" its tracing state
from the global state array. That is, if *any* existing vCPU has an
event enabled, new vCPUs will have too.

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Message-id: 147428970768.15111.7664565956870423529.stgit@fimbulvetr.bsc.es
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/trace/control-target.c b/trace/control-target.c
index 72081e2a34..3b7d99b44c 100644
--- a/trace/control-target.c
+++ b/trace/control-target.c
@@ -81,3 +81,40 @@ void trace_event_set_vcpu_state_dynamic(CPUState *vcpu,
         }
     }
 }
+
+static bool adding_first_cpu(void)
+{
+    CPUState *cpu;
+    size_t count = 0;
+    CPU_FOREACH(cpu) {
+        count++;
+        if (count > 1) {
+            return false;
+        }
+    }
+    return true;
+}
+
+void trace_init_vcpu(CPUState *vcpu)
+{
+    TraceEvent *ev = NULL;
+
+    while ((ev = trace_event_pattern("*", ev)) != NULL) {
+        if (trace_event_is_vcpu(ev) &&
+            trace_event_get_state_static(ev) &&
+            trace_event_get_state_dynamic(ev)) {
+            TraceEventID id = trace_event_get_id(ev);
+            if (adding_first_cpu()) {
+                /* check preconditions */
+                assert(trace_events_dstate[id] == 1);
+                /* disable early-init state ... */
+                trace_events_dstate[id] = 0;
+                trace_events_enabled_count--;
+                /* ... and properly re-enable */
+                trace_event_set_vcpu_state_dynamic(vcpu, ev, true);
+            } else {
+                trace_event_set_vcpu_state_dynamic(vcpu, ev, true);
+            }
+        }
+    }
+}