[PATCH] trace-cmd listen: Add documentation on vsocket usage

[Steven Rostedt <rostedt@goodmis.org>]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

Document the -V option for trace-cmd listen/record in both the usage and the
man pages.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
[ Depends on: https://lore.kernel.org/all/20220412042739.836516-1-rostedt@goodmis.org/ ]

 Documentation/trace-cmd/trace-cmd-listen.1.txt | 4 ++++
 Documentation/trace-cmd/trace-cmd-record.1.txt | 8 ++++++++
 tracecmd/trace-usage.c                         | 2 ++
 3 files changed, 14 insertions(+)

diff --git a/Documentation/trace-cmd/trace-cmd-listen.1.txt b/Documentation/trace-cmd/trace-cmd-listen.1.txt
index aa6a307f..7c6093ba 100644
--- a/Documentation/trace-cmd/trace-cmd-listen.1.txt
+++ b/Documentation/trace-cmd/trace-cmd-listen.1.txt
@@ -26,6 +26,10 @@ OPTIONS
     This options causes trace-cmd listen to go into a daemon mode and run in
     the background.
 
+*-V*::
+    Listen on a vsocket instead. This is useful for tracing between host and
+    guest VMs.
+
 *-d* 'dir'::
     This option specifies a directory to write the data files into.
 
diff --git a/Documentation/trace-cmd/trace-cmd-record.1.txt b/Documentation/trace-cmd/trace-cmd-record.1.txt
index 426e856b..6b8e3b4a 100644
--- a/Documentation/trace-cmd/trace-cmd-record.1.txt
+++ b/Documentation/trace-cmd/trace-cmd-record.1.txt
@@ -259,6 +259,14 @@ OPTIONS
     Note: This option is not supported with latency tracer plugins:
       wakeup, wakeup_rt, irqsoff, preemptoff and preemptirqsoff
 
+*-V* 'cid:port'::
+    If recording on a guest VM and the host is running *trace-cmd listen* with
+    the *-V* option as well, or if this is recording on the host, and a guest
+    in running *trace-cmd listen* with the *-V* option, then connect to the
+    listener (the same as connecting with the *-N* option via the network).
+    This has the same limitations as the *-N* option above with respect to
+    latency tracer plugins.
+
 *-t*::
     This option is used with *-N*, when there's a need to send the live data
     with TCP packets instead of UDP. Although TCP is not nearly as fast as
diff --git a/tracecmd/trace-usage.c b/tracecmd/trace-usage.c
index 20995fab..ec637655 100644
--- a/tracecmd/trace-usage.c
+++ b/tracecmd/trace-usage.c
@@ -44,6 +44,7 @@ static struct usage_help usage_help[] = {
 		"          -s sleep interval between recording (in usecs) [default: 1000]\n"
 		"          -S used with --profile, to enable only events in command line\n"
 		"          -N host:port to connect to (see listen)\n"
+		"          -V cid:port to connect to via vsocket (see listen)\n"
 		"          -t used with -N, forces use of tcp in live trace\n"
 		"          -b change kernel buffersize (in kilobytes per CPU)\n"
 		"          -B create sub buffer and following events will be enabled here\n"
@@ -318,6 +319,7 @@ static struct usage_help usage_help[] = {
 		"          Creates a socket to listen for clients.\n"
 		"          -p port number to listen on.\n"
 		"          -D run in daemon mode.\n"
+		"          -V listen on a vsocket instead.\n"
 		"          -o file name to use for clients.\n"
 		"          -d directory to store client files.\n"
 		"          -l logfile to write messages to.\n"
-- 
2.35.1