qdev-properties-system.c: Allow vlan or netdev for -device, not both

[qemu.git] / docs / tracing.txt

diff --git a/docs/tracing.txt b/docs/tracing.txt
index cf53c173ec17ac6e516202f9bb9729a9f8f5fe9f..bfc261bcaf595163d8fa2316e84c04e9c9efae13 100644 (file)
--- a/docs/tracing.txt
+++ b/docs/tracing.txt
@@ -175,6 +175,22 @@ 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.
+
 ==== Monitor commands ====
 
 * trace-file on|off|flush|set <path>
@@ -209,7 +225,7 @@ probes:
     scripts/tracetool --dtrace --stap \
                       --binary path/to/qemu-binary \
                       --target-type system \
-                      --target-arch x86_64 \
+                      --target-name x86_64 \
                       <trace-events >qemu.stp
 
 == Trace event properties ==