trace: Add per-vCPU tracing states for events with the 'vcpu' property

Each vCPU gets a 'trace_dstate' bitmap to control the per-vCPU dynamic
tracing state of events with the 'vcpu' property.
Signed-off-by: NLluís Vilanova <vilanova@ac.upc.edu>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

bsd-user/main.c

@@ -1131,6 +1131,7 @@ int main(int argc, char **argv)
         gdbserver_start (gdbstub_port);
         gdb_handlesig(cpu, 0);
     }
+    trace_init_vcpu_events();
     cpu_loop(env);
     /* never exits */
     return 0;

include/qom/cpu.h

@@ -24,8 +24,10 @@
 #include "disas/bfd.h"
 #include "exec/hwaddr.h"
 #include "exec/memattrs.h"
+#include "qemu/bitmap.h"
 #include "qemu/queue.h"
 #include "qemu/thread.h"
+#include "trace/generated-events.h"
 
 typedef int (*WriteCoreDumpFunction)(const void *buf, size_t size,
                                      void *opaque);
@@ -280,6 +282,7 @@ struct qemu_work_item {
  * @kvm_fd: vCPU file descriptor for KVM.
  * @work_mutex: Lock to prevent multiple access to queued_work_*.
  * @queued_work_first: First asynchronous work pending.
+ * @trace_dstate: Dynamic tracing state of events for this vCPU (bitmask).
  *
  * State of one CPU core or thread.
  */
@@ -347,6 +350,9 @@ struct CPUState {
     struct KVMState *kvm_state;
     struct kvm_run *kvm_run;
 
+    /* Used for events with 'vcpu' and *without* the 'disabled' properties */
+    DECLARE_BITMAP(trace_dstate, TRACE_VCPU_EVENT_COUNT);
+
     /* TODO Move common fields from CPUArchState here. */
     int cpu_index; /* used by alpha TCG */
     uint32_t halted; /* used by alpha, cris, ppc TCG */

linux-user/main.c

@@ -4810,6 +4810,7 @@ int main(int argc, char **argv, char **envp)
         }
         gdb_handlesig(cpu, 0);
     }
+    trace_init_vcpu_events();
     cpu_loop(env);
     /* never exits */
     return 0;

qom/cpu.c

@@ -345,6 +345,7 @@ static void cpu_common_initfn(Object *obj)
     qemu_mutex_init(&cpu->work_mutex);
     QTAILQ_INIT(&cpu->breakpoints);
     QTAILQ_INIT(&cpu->watchpoints);
+    bitmap_zero(cpu->trace_dstate, TRACE_VCPU_EVENT_COUNT);
 }
 
 static void cpu_common_finalize(Object *obj)

stubs/Makefile.objs

@@ -30,6 +30,7 @@ stub-obj-y += runstate-check.o
 stub-obj-y += set-fd-handler.o
 stub-obj-y += slirp.o
 stub-obj-y += sysbus.o
+stub-obj-y += trace-control.o
 stub-obj-y += uuid.o
 stub-obj-y += vm-stop.o
 stub-obj-y += vmstate.o

stubs/trace-control.c

+/*
+ * Interface for configuring and controlling the state of tracing events.
+ *
+ * Copyright (C) 2014-2016 Lluís Vilanova <vilanova@ac.upc.edu>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "trace/control.h"
+
+
+void trace_event_set_state_dynamic(TraceEvent *ev, bool state)
+{
+    TraceEventID id;
+    assert(trace_event_get_state_static(ev));
+    id = trace_event_get_id(ev);
+    trace_events_enabled_count += state - trace_events_dstate[id];
+    trace_events_dstate[id] = state;
+}
+
+void trace_event_set_vcpu_state_dynamic(CPUState *vcpu,
+                                        TraceEvent *ev, bool state)
+{
+    /* should never be called on non-target binaries */
+    abort();
+}

trace/Makefile.objs

@@ -15,6 +15,7 @@ $(BUILD_DIR)/trace-events-all: $(trace-events-y:%=$(SRC_PATH)/%)
 # Auto-generated event descriptions for LTTng ust code
 
 ifeq ($(findstring ust,$(TRACE_BACKENDS)),ust)
+
 $(obj)/generated-ust-provider.h: $(obj)/generated-ust-provider.h-timestamp
 	@cmp $< $@ >/dev/null 2>&1 || cp $< $@
 $(obj)/generated-ust-provider.h-timestamp: $(BUILD_DIR)/trace-events-all $(tracetool-y)
@@ -33,6 +34,7 @@ $(obj)/generated-ust.c-timestamp: $(BUILD_DIR)/trace-events-all $(tracetool-y)
 
 $(obj)/generated-events.h: $(obj)/generated-ust-provider.h
 $(obj)/generated-events.c: $(obj)/generated-ust.c
+
 endif
 
 ######################################################################
@@ -91,6 +93,7 @@ $(obj)/generated-tracers.o: $(obj)/generated-tracers.c $(obj)/generated-tracers.
 # but that gets picked up by QEMU's Makefile as an external dependency
 # rule file. So we use '.dtrace' instead
 ifeq ($(findstring dtrace,$(TRACE_BACKENDS)),dtrace)
+
 $(obj)/generated-tracers-dtrace.dtrace: $(obj)/generated-tracers-dtrace.dtrace-timestamp
 	@cmp $< $@ >/dev/null 2>&1 || cp $< $@
 $(obj)/generated-tracers-dtrace.dtrace-timestamp: $(BUILD_DIR)/trace-events-all $(BUILD_DIR)/config-host.mak $(tracetool-y)
@@ -155,4 +158,5 @@ util-obj-$(CONFIG_TRACE_SIMPLE) += simple.o generated-tracers.o
 util-obj-$(CONFIG_TRACE_FTRACE) += ftrace.o
 util-obj-$(CONFIG_TRACE_UST) += generated-ust.o
 util-obj-y += control.o
+target-obj-y += control-target.o
 util-obj-y += qmp.o

trace/control-internal.h

@@ -10,8 +10,13 @@
 #ifndef TRACE__CONTROL_INTERNAL_H
 #define TRACE__CONTROL_INTERNAL_H
 
+#include <stddef.h>                     /* size_t */
+
+#include "qom/cpu.h"
+
+
 extern TraceEvent trace_events[];
-extern bool trace_events_dstate[];
+extern uint16_t trace_events_dstate[];
 extern int trace_events_enabled_count;
 
 
@@ -74,13 +79,24 @@ static inline bool trace_event_get_state_dynamic(TraceEvent *ev)
     return trace_event_get_state_dynamic_by_id(id);
 }
 
-static inline void trace_event_set_state_dynamic(TraceEvent *ev, bool state)
+static inline bool trace_event_get_vcpu_state_dynamic_by_vcpu_id(CPUState *vcpu,
+                                                                 TraceEventVCPUID id)
 {
-    int id = trace_event_get_id(ev);
-    assert(ev != NULL);
-    assert(trace_event_get_state_static(ev));
-    trace_events_enabled_count += state - trace_events_dstate[id];
-    trace_events_dstate[id] = state;
+    /* it's on fast path, avoid consistency checks (asserts) */
+    if (unlikely(trace_events_enabled_count)) {
+        return test_bit(id, vcpu->trace_dstate);
+    } else {
+        return false;
+    }
+}
+
+static inline bool trace_event_get_vcpu_state_dynamic(CPUState *vcpu,
+                                                      TraceEvent *ev)
+{
+    TraceEventVCPUID id;
+    assert(trace_event_is_vcpu(ev));
+    id = trace_event_get_vcpu_id(ev);
+    return trace_event_get_vcpu_state_dynamic_by_vcpu_id(vcpu, id);
 }
 
 #endif /* TRACE__CONTROL_INTERNAL_H */

trace/control-target.c

+/*
+ * Interface for configuring and controlling the state of tracing events.
+ *
+ * Copyright (C) 2014-2016 Lluís Vilanova <vilanova@ac.upc.edu>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "cpu.h"
+#include "trace/control.h"
+#include "translate-all.h"
+
+
+void trace_event_set_state_dynamic(TraceEvent *ev, bool state)
+{
+    CPUState *vcpu;
+    assert(trace_event_get_state_static(ev));
+    if (trace_event_is_vcpu(ev)) {
+        CPU_FOREACH(vcpu) {
+            trace_event_set_vcpu_state_dynamic(vcpu, ev, state);
+        }
+    } else {
+        TraceEventID id = trace_event_get_id(ev);
+        trace_events_enabled_count += state - trace_events_dstate[id];
+        trace_events_dstate[id] = state;
+    }
+}
+
+void trace_event_set_vcpu_state_dynamic(CPUState *vcpu,
+                                        TraceEvent *ev, bool state)
+{
+    TraceEventID id;
+    TraceEventVCPUID vcpu_id;
+    bool state_pre;
+    assert(trace_event_get_state_static(ev));
+    assert(trace_event_is_vcpu(ev));
+    id = trace_event_get_id(ev);
+    vcpu_id = trace_event_get_vcpu_id(ev);
+    state_pre = test_bit(vcpu_id, vcpu->trace_dstate);
+    if (state_pre != state) {
+        if (state) {
+            trace_events_enabled_count++;
+            set_bit(vcpu_id, vcpu->trace_dstate);
+            trace_events_dstate[id]++;
+        } else {
+            trace_events_enabled_count--;
+            clear_bit(vcpu_id, vcpu->trace_dstate);
+            trace_events_dstate[id]--;
+        }
+    }
+}

trace/control.c

 /*
  * Interface for configuring and controlling the state of tracing events.
  *
- * Copyright (C) 2011-2014 Lluís Vilanova <vilanova@ac.upc.edu>
+ * Copyright (C) 2011-2016 Lluís Vilanova <vilanova@ac.upc.edu>
  *
  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  * See the COPYING file in the top-level directory.
@@ -25,7 +25,14 @@
 #include "monitor/monitor.h"
 
 int trace_events_enabled_count;
-bool trace_events_dstate[TRACE_EVENT_COUNT];
+/*
+ * Interpretation depends on wether the event has the 'vcpu' property:
+ * - false: Boolean value indicating whether the event is active.
+ * - true : Integral counting the number of vCPUs that have this event enabled.
+ */
+uint16_t trace_events_dstate[TRACE_EVENT_COUNT];
+/* Marks events for late vCPU state init */
+static bool trace_events_dstate_init[TRACE_EVENT_COUNT];
 
 QemuOptsList qemu_trace_opts = {
     .name = "trace",
@@ -135,7 +142,10 @@ static void do_trace_enable_events(const char *line_buf)
         TraceEvent *ev = NULL;
         while ((ev = trace_event_pattern(line_ptr, ev)) != NULL) {
             if (trace_event_get_state_static(ev)) {
+                /* start tracing */
                 trace_event_set_state_dynamic(ev, enable);
+                /* mark for late vCPU init */
+                trace_events_dstate_init[ev->id] = true;
             }
         }
     } else {
@@ -147,7 +157,10 @@ static void do_trace_enable_events(const char *line_buf)
             error_report("WARNING: trace event '%s' is not traceable",
                          line_ptr);
         } else {
+            /* start tracing */
             trace_event_set_state_dynamic(ev, enable);
+            /* mark for late vCPU init */
+            trace_events_dstate_init[ev->id] = true;
         }
     }
 }
@@ -257,3 +270,15 @@ char *trace_opt_parse(const char *optarg)
 
     return trace_file;
 }
+
+void trace_init_vcpu_events(void)
+{
+    TraceEvent *ev = NULL;
+    while ((ev = trace_event_pattern("*", ev)) != NULL) {
+        if (trace_event_is_vcpu(ev) &&
+            trace_event_get_state_static(ev) &&
+            trace_events_dstate_init[ev->id]) {
+            trace_event_set_state_dynamic(ev, true);
+        }
+    }
+}

trace/control.h

@@ -123,6 +123,23 @@ static const char * trace_event_get_name(TraceEvent *ev);
 #define trace_event_get_state(id)                       \
     ((id ##_ENABLED) && trace_event_get_state_dynamic_by_id(id))
 
+/**
+ * trace_event_get_vcpu_state:
+ * @vcpu: Target vCPU.
+ * @id: Event identifier (TraceEventID).
+ * @vcpu_id: Per-vCPU event identifier (TraceEventVCPUID).
+ *
+ * Get the tracing state of an event (both static and dynamic) for the given
+ * vCPU.
+ *
+ * If the event has the disabled property, the check will have no performance
+ * impact.
+ *
+ * As a down side, you must always use an immediate #TraceEventID value.
+ */
+#define trace_event_get_vcpu_state(vcpu, id, vcpu_id)                   \
+    ((id ##_ENABLED) && trace_event_get_vcpu_state_dynamic_by_vcpu_id(vcpu, vcpu_id))
+
 /**
  * trace_event_get_state_static:
  * @id: Event identifier.
@@ -138,9 +155,18 @@ static bool trace_event_get_state_static(TraceEvent *ev);
  * trace_event_get_state_dynamic:
  *
  * Get the dynamic tracing state of an event.
+ *
+ * If the event has the 'vcpu' property, gets the OR'ed state of all vCPUs.
  */
 static bool trace_event_get_state_dynamic(TraceEvent *ev);
 
+/**
+ * trace_event_get_vcpu_state_dynamic:
+ *
+ * Get the dynamic tracing state of an event for the given vCPU.
+ */
+static bool trace_event_get_vcpu_state_dynamic(CPUState *vcpu, TraceEvent *ev);
+
 /**
  * trace_event_set_state:
  *
@@ -154,14 +180,39 @@ static bool trace_event_get_state_dynamic(TraceEvent *ev);
         }                                               \
     } while (0)
 
+/**
+ * trace_event_set_vcpu_state:
+ *
+ * Set the tracing state of an event for the given vCPU (only if not disabled).
+ */
+#define trace_event_set_vcpu_state(vcpu, id, state)                     \
+    do {                                                                \
+        if ((id ##_ENABLED)) {                                          \
+            TraceEvent *_e = trace_event_id(id);                        \
+            trace_event_set_vcpu_state_dynamic(vcpu, _e, state);        \
+        }                                                               \
+    } while (0)
+
 /**
  * trace_event_set_state_dynamic:
  *
  * Set the dynamic tracing state of an event.
  *
+ * If the event has the 'vcpu' property, sets the state on all vCPUs.
+ *
  * Pre-condition: trace_event_get_state_static(ev) == true
  */
-static void trace_event_set_state_dynamic(TraceEvent *ev, bool state);
+void trace_event_set_state_dynamic(TraceEvent *ev, bool state);
+
+/**
+ * trace_event_set_vcpu_state_dynamic:
+ *
+ * Set the dynamic tracing state of an event for the given vCPU.
+ *
+ * Pre-condition: trace_event_get_vcpu_state_static(ev) == true
+ */
+void trace_event_set_vcpu_state_dynamic(CPUState *vcpu,
+                                        TraceEvent *ev, bool state);
 
 
 
@@ -218,6 +269,15 @@ extern QemuOptsList qemu_trace_opts;
  */
 char *trace_opt_parse(const char *optarg);
 
+/**
+ * trace_init_vcpu_events:
+ *
+ * Re-synchronize initial event state with vCPUs (which can be created after
+ * trace_init_events()).
+ */
+void trace_init_vcpu_events(void);
+
+
 #include "trace/control-internal.h"
 
 #endif /* TRACE__CONTROL_H */

translate-all.h

@@ -19,6 +19,9 @@
 #ifndef TRANSLATE_ALL_H
 #define TRANSLATE_ALL_H
 
+#include "exec/exec-all.h"
+
+
 /* translate-all.c */
 void tb_invalidate_phys_page_fast(tb_page_addr_t start, int len);
 void tb_invalidate_phys_page_range(tb_page_addr_t start, tb_page_addr_t end,

vl.c

@@ -4598,6 +4598,7 @@ int main(int argc, char **argv, char **envp)
 
     os_setup_post();
 
+    trace_init_vcpu_events();
     main_loop();
     replay_disable_events();