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diff --git a/docs/tracing.txt b/docs/tracing.txt
index cf53c173ec..e14bb6dccc 100644
--- a/docs/tracing.txt
+++ b/docs/tracing.txt
@@ -9,7 +9,7 @@ for debugging, profiling, and observing execution.
 
 1. Build with the 'simple' trace backend:
 
-    ./configure --enable-trace-backend=simple
+    ./configure --enable-trace-backends=simple
     make
 
 2. Create a file with the events you want to trace:
@@ -23,20 +23,50 @@ for debugging, profiling, and observing execution.
 
 4. Pretty-print the binary trace file:
 
-    ./scripts/simpletrace.py trace-events trace-*
+    ./scripts/simpletrace.py trace-events-all trace-* # Override * with QEMU <pid>
 
 == Trace events ==
 
-There is a set of static trace events declared in the "trace-events" source
-file.  Each trace event declaration names the event, its arguments, and the
-format string which can be used for pretty-printing:
+=== Sub-directory setup ===
 
-    qemu_vmalloc(size_t size, void *ptr) "size %zu ptr %p"
-    qemu_vfree(void *ptr) "ptr %p"
+Each directory in the source tree can declare a set of static trace events
+in a local "trace-events" file. All directories which contain "trace-events"
+files must be listed in the "trace-events-subdirs" make variable in the top
+level Makefile.objs. During build, the "trace-events" file in each listed
+subdirectory will be processed by the "tracetool" script to generate code for
+the trace events.
+
+The individual "trace-events" files are merged into a "trace-events-all" file,
+which is also installed into "/usr/share/qemu" with the name "trace-events".
+This merged file is to be used by the "simpletrace.py" script to later analyse
+traces in the simpletrace data format.
+
+In the sub-directory the following files will be automatically generated
+
+ - trace.c - the trace event state declarations
+ - trace.h - the trace event enums and probe functions
+ - trace-dtrace.h - DTrace event probe specification
+ - trace-dtrace.dtrace - DTrace event probe helper declaration
+ - trace-dtrace.o - binary DTrace provider (generated by dtrace)
+ - trace-ust.h - UST event probe helper declarations
+
+Source files in the sub-directory should #include the local 'trace.h' file,
+without any sub-directory path prefix. eg io/channel-buffer.c would do
+
+  #include "trace.h"
+
+To access the 'io/trace.h' file. While it is possible to include a trace.h
+file from outside a source files' own sub-directory, this is discouraged in
+general. It is strongly preferred that all events be declared directly in
+the sub-directory that uses them. The only exception is where there are some
+shared trace events defined in the top level directory trace-events file.
+The top level directory generates trace files with a filename prefix of
+"trace-root" instead of just "trace". This is to avoid ambiguity between
+a trace.h in the current directory, vs the top level directory.
+
+=== Using trace events ===
 
-The "trace-events" file is processed by the "tracetool" script during build to
-generate code for the trace events.  Trace events are invoked directly from
-source code like this:
+Trace events are invoked directly from source code like this:
 
     #include "trace.h"  /* needed for trace event prototype */
     
@@ -79,6 +109,13 @@ Format strings should reflect the types defined in the trace event.  Take
 special care to use PRId64 and PRIu64 for int64_t and uint64_t types,
 respectively.  This ensures portability between 32- and 64-bit platforms.
 
+Each event declaration will start with the event name, then its arguments,
+finally a format string for pretty-printing. For example:
+
+    qemu_vmalloc(size_t size, void *ptr) "size %zu ptr %p"
+    qemu_vfree(void *ptr) "ptr %p"
+
+
 === Hints for adding new trace events ===
 
 1. Trace state changes in the code.  Interesting points in the code usually
@@ -139,27 +176,30 @@ events are not tightly coupled to a specific trace backend, such as LTTng or
 SystemTap.  Support for trace backends can be added by extending the "tracetool"
 script.
 
-The trace backend is chosen at configure time and only one trace backend can
-be built into the binary:
+The trace backends are chosen at configure time:
 
-    ./configure --trace-backend=simple
+    ./configure --enable-trace-backends=simple
 
 For a list of supported trace backends, try ./configure --help or see below.
+If multiple backends are enabled, the trace is sent to them all.
+
+If no backends are explicitly selected, configure will default to the
+"log" backend.
 
 The following subsections describe the supported trace backends.
 
 === Nop ===
 
 The "nop" backend generates empty trace event functions so that the compiler
-can optimize out trace events completely.  This is the default and imposes no
-performance penalty.
+can optimize out trace events completely.  This imposes no performance
+penalty.
 
 Note that regardless of the selected trace backend, events with the "disable"
 property will be generated with the "nop" backend.
 
-=== Stderr ===
+=== Log ===
 
-The "stderr" backend sends trace events directly to standard error.  This
+The "log" backend sends trace events directly to standard error.  This
 effectively turns trace events into debug printfs.
 
 This is the simplest backend and can be used together with existing code that
@@ -172,8 +212,33 @@ source tree.  It may not be as powerful as platform-specific or third-party
 trace backends but it is portable.  This is the recommended trace backend
 unless you have specific needs for more advanced backends.
 
-The "simple" backend currently does not capture string arguments, it simply
-records the char* pointer value instead of the string that is pointed to.
+=== Ftrace ===
+
+The "ftrace" backend writes trace data to ftrace marker. This effectively
+sends trace events to ftrace ring buffer, and you can compare qemu trace
+data and kernel(especially kvm.ko when using KVM) trace data.
+
+if you use KVM, enable kvm events in ftrace:
+
+   # echo 1 > /sys/kernel/debug/tracing/events/kvm/enable
+
+After running qemu by root user, you can get the trace:
+
+   # cat /sys/kernel/debug/tracing/trace
+
+Restriction: "ftrace" backend is restricted to Linux only.
+
+=== Syslog ===
+
+The "syslog" backend sends trace events using the POSIX syslog API. The log
+is opened specifying the LOG_DAEMON facility and LOG_PID option (so events
+are tagged with the pid of the particular QEMU process that generated
+them). All events are logged at LOG_INFO level.
+
+NOTE: syslog may squash duplicate consecutive trace events and apply rate
+      limiting.
+
+Restriction: "syslog" backend is restricted to POSIX compliant OS.
 
 ==== Monitor commands ====
 
@@ -183,12 +248,12 @@ records the char* pointer value instead of the string that is pointed to.
 ==== Analyzing trace files ====
 
 The "simple" backend produces binary trace files that can be formatted with the
-simpletrace.py script.  The script takes the "trace-events" file and the binary
-trace:
+simpletrace.py script.  The script takes the "trace-events-all" file and the
+binary trace:
 
-    ./scripts/simpletrace.py trace-events trace-12345
+    ./scripts/simpletrace.py trace-events-all trace-12345
 
-You must ensure that the same "trace-events" file was used to build QEMU,
+You must ensure that the same "trace-events-all" file was used to build QEMU,
 otherwise trace event declarations may have changed and output will not be
 consistent.
 
@@ -198,6 +263,42 @@ The "ust" backend uses the LTTng Userspace Tracer library.  There are no
 monitor commands built into QEMU, instead UST utilities should be used to list,
 enable/disable, and dump traces.
 
+Package lttng-tools is required for userspace tracing. You must ensure that the
+current user belongs to the "tracing" group, or manually launch the
+lttng-sessiond daemon for the current user prior to running any instance of
+QEMU.
+
+While running an instrumented QEMU, LTTng should be able to list all available
+events:
+
+    lttng list -u
+
+Create tracing session:
+
+    lttng create mysession
+
+Enable events:
+
+    lttng enable-event qemu:g_malloc -u
+
+Where the events can either be a comma-separated list of events, or "-a" to
+enable all tracepoint events. Start and stop tracing as needed:
+
+    lttng start
+    lttng stop
+
+View the trace:
+
+    lttng view
+
+Destroy tracing session:
+
+    lttng destroy
+
+Babeltrace can be used at any later time to view the trace:
+
+    babeltrace $HOME/lttng-traces/mysession-<date>-<time>
+
 === SystemTap ===
 
 The "dtrace" backend uses DTrace sdt probes but has only been tested with
@@ -206,15 +307,15 @@ is generated to make use in scripts more convenient.  This step can also be
 performed manually after a build in order to change the binary name in the .stp
 probes:
 
-    scripts/tracetool --dtrace --stap \
-                      --binary path/to/qemu-binary \
-                      --target-type system \
-                      --target-arch x86_64 \
-                      <trace-events >qemu.stp
+    scripts/tracetool.py --backends=dtrace --format=stap \
+                         --binary path/to/qemu-binary \
+                         --target-type system \
+                         --target-name x86_64 \
+                         <trace-events-all >qemu.stp
 
 == Trace event properties ==
 
-Each event in the "trace-events" file can be prefixed with a space-separated
+Each event in the "trace-events-all" file can be prefixed with a space-separated
 list of zero or more of the following event properties.
 
 === "disable" ===
@@ -226,7 +327,7 @@ programmatically disabled.
 In this case you should declare such event with the "disable" property. This
 will effectively disable the event at compile time (by using the "nop" backend),
 thus having no performance impact at all on regular builds (i.e., unless you
-edit the "trace-events" file).
+edit the "trace-events-all" file).
 
 In addition, there might be cases where relatively complex computations must be
 performed to generate values that are only used as arguments for a trace
@@ -255,3 +356,84 @@ guard such computations and avoid its compilation when the event is disabled:
 You can check both if the event has been disabled and is dynamically enabled at
 the same time using the 'trace_event_get_state' routine (see header
 "trace/control.h" for more information).
+
+=== "tcg" ===
+
+Guest code generated by TCG can be traced by defining an event with the "tcg"
+event property. Internally, this property generates two events:
+"<eventname>_trans" to trace the event at translation time, and
+"<eventname>_exec" to trace the event at execution time.
+
+Instead of using these two events, you should instead use the function
+"trace_<eventname>_tcg" during translation (TCG code generation). This function
+will automatically call "trace_<eventname>_trans", and will generate the
+necessary TCG code to call "trace_<eventname>_exec" during guest code execution.
+
+Events with the "tcg" property can be declared in the "trace-events" file with a
+mix of native and TCG types, and "trace_<eventname>_tcg" will gracefully forward
+them to the "<eventname>_trans" and "<eventname>_exec" events. Since TCG values
+are not known at translation time, these are ignored by the "<eventname>_trans"
+event. Because of this, the entry in the "trace-events" file needs two printing
+formats (separated by a comma):
+
+    tcg foo(uint8_t a1, TCGv_i32 a2) "a1=%d", "a1=%d a2=%d"
+
+For example:
+
+    #include "trace-tcg.h"
+    
+    void some_disassembly_func (...)
+    {
+        uint8_t a1 = ...;
+        TCGv_i32 a2 = ...;
+        trace_foo_tcg(a1, a2);
+    }
+
+This will immediately call:
+
+    void trace_foo_trans(uint8_t a1);
+
+and will generate the TCG code to call:
+
+    void trace_foo(uint8_t a1, uint32_t a2);
+
+=== "vcpu" ===
+
+Identifies events that trace vCPU-specific information. It implicitly adds a
+"CPUState*" argument, and extends the tracing print format to show the vCPU
+information. If used together with the "tcg" property, it adds a second
+"TCGv_env" argument that must point to the per-target global TCG register that
+points to the vCPU when guest code is executed (usually the "cpu_env" variable).
+
+The following example events:
+
+    foo(uint32_t a) "a=%x"
+    vcpu bar(uint32_t a) "a=%x"
+    tcg vcpu baz(uint32_t a) "a=%x", "a=%x"
+
+Can be used as:
+
+    #include "trace-tcg.h"
+    
+    CPUArchState *env;
+    TCGv_ptr cpu_env;
+    
+    void some_disassembly_func(...)
+    {
+        /* trace emitted at this point */
+        trace_foo(0xd1);
+        /* trace emitted at this point */
+        trace_bar(ENV_GET_CPU(env), 0xd2);
+        /* trace emitted at this point (env) and when guest code is executed (cpu_env) */
+        trace_baz_tcg(ENV_GET_CPU(env), cpu_env, 0xd3);
+    }
+
+If the translating vCPU has address 0xc1 and code is later executed by vCPU
+0xc2, this would be an example output:
+
+    // at guest code translation
+    foo a=0xd1
+    bar cpu=0xc1 a=0xd2
+    baz_trans cpu=0xc1 a=0xd3
+    // at guest code execution
+    baz_exec cpu=0xc2 a=0xd3