docs: Split qemu-pr-helper documentation into tools manual

Split the documentation of the qemu-pr-helper binary into the tools
manual, and give it a manpage like our other standalone executables.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

docs/meson.build

@@ -60,6 +60,7 @@ if build_docs
     'tools': {
         'qemu-img.1': (have_tools ? 'man1' : ''),
         'qemu-nbd.8': (have_tools ? 'man8' : ''),
+        'qemu-pr-helper.8': (have_tools ? 'man8' : ''),
         'qemu-trace-stap.1': (config_host.has_key('CONFIG_TRACE_SYSTEMTAP') ? 'man1' : ''),
         'virtfs-proxy-helper.1': (have_virtfs_proxy_helper ? 'man1' : ''),
         'virtiofsd.1': (have_virtiofsd ? 'man1' : ''),

docs/system/pr-manager.rst

@@ -50,39 +50,11 @@ Alternatively, using ``-blockdev``::
           -blockdev node-name=hd,driver=raw,file.driver=host_device,file.filename=/dev/sdb,file.pr-manager=helper0
           -device scsi-block,drive=hd
 
-----------------------------------
-Invoking :program:`qemu-pr-helper`
-----------------------------------
-
-QEMU provides an implementation of the persistent reservation helper,
-called :program:`qemu-pr-helper`.  The helper should be started as a
-system service and supports the following option:
-
--d, --daemon              run in the background
--q, --quiet               decrease verbosity
--v, --verbose             increase verbosity
--f, --pidfile=path        PID file when running as a daemon
--k, --socket=path         path to the socket
--T, --trace=trace-opts    tracing options
-
-By default, the socket and PID file are placed in the runtime state
-directory, for example :file:`/var/run/qemu-pr-helper.sock` and
-:file:`/var/run/qemu-pr-helper.pid`.  The PID file is not created
-unless :option:`-d` is passed too.
-
-:program:`qemu-pr-helper` can also use the systemd socket activation
-protocol.  In this case, the systemd socket unit should specify a
-Unix stream socket, like this::
-
-    [Socket]
-    ListenStream=/var/run/qemu-pr-helper.sock
-
-After connecting to the socket, :program:`qemu-pr-helper`` can optionally drop
-root privileges, except for those capabilities that are needed for
-its operation.  To do this, add the following options:
-
--u, --user=user           user to drop privileges to
--g, --group=group         group to drop privileges to
+You will also need to ensure that the helper program
+:command:`qemu-pr-helper` is running, and that it has been
+set up to use the same socket filename as your QEMU commandline
+specifies. See the qemu-pr-helper documentation or manpage for
+further details.
 
 ---------------------------------------------
 Multipath devices and persistent reservations

docs/tools/conf.py

@@ -22,6 +22,8 @@ man_pages = [
      ['Fabrice Bellard'], 1),
     ('qemu-nbd', 'qemu-nbd', u'QEMU Disk Network Block Device Server',
      ['Anthony Liguori <anthony@codemonkey.ws>'], 8),
+    ('qemu-pr-helper', 'qemu-pr-helper', 'QEMU persistent reservation helper',
+     [], 8),
     ('qemu-trace-stap', 'qemu-trace-stap', u'QEMU SystemTap trace tool',
      [], 1),
     ('virtfs-proxy-helper', 'virtfs-proxy-helper',

docs/tools/index.rst

@@ -12,6 +12,7 @@ Contents:
 
    qemu-img
    qemu-nbd
+   qemu-pr-helper
    qemu-trace-stap
    virtfs-proxy-helper
    virtiofsd

docs/tools/qemu-pr-helper.rst

@@ -0,0 +1,90 @@
+QEMU persistent reservation helper
+==================================
+
+Synopsis
+--------
+
+**qemu-pr-helper** [*OPTION*]
+
+Description
+-----------
+
+Implements the persistent reservation helper for QEMU.
+
+SCSI persistent reservations allow restricting access to block devices
+to specific initiators in a shared storage setup.  When implementing
+clustering of virtual machines, it is a common requirement for virtual
+machines to send persistent reservation SCSI commands.  However,
+the operating system restricts sending these commands to unprivileged
+programs because incorrect usage can disrupt regular operation of the
+storage fabric. QEMU's SCSI passthrough devices ``scsi-block``
+and ``scsi-generic`` support passing guest persistent reservation
+requests to a privileged external helper program. :program:`qemu-pr-helper`
+is that external helper; it creates a socket which QEMU can
+connect to to communicate with it.
+
+If you want to run VMs in a setup like this, this helper should be
+started as a system service, and you should read the QEMU manual
+section on "persistent reservation managers" to find out how to
+configure QEMU to connect to the socket created by
+:program:`qemu-pr-helper`.
+
+After connecting to the socket, :program:`qemu-pr-helper` can
+optionally drop root privileges, except for those capabilities that
+are needed for its operation.
+
+:program:`qemu-pr-helper` can also use the systemd socket activation
+protocol.  In this case, the systemd socket unit should specify a
+Unix stream socket, like this::
+
+    [Socket]
+    ListenStream=/var/run/qemu-pr-helper.sock
+
+Options
+-------
+
+.. program:: qemu-pr-helper
+
+.. option:: -d, --daemon
+
+  run in the background (and create a PID file)
+
+.. option:: -q, --quiet
+
+  decrease verbosity
+
+.. option:: -v, --verbose
+
+  increase verbosity
+
+.. option:: -f, --pidfile=PATH
+
+  PID file when running as a daemon. By default the PID file
+  is created in the system runtime state directory, for example
+  :file:`/var/run/qemu-pr-helper.pid`.
+
+.. option:: -k, --socket=PATH
+
+  path to the socket. By default the socket is created in
+  the system runtime state directory, for example
+  :file:`/var/run/qemu-pr-helper.sock`.
+
+.. option:: -T, --trace [[enable=]PATTERN][,events=FILE][,file=FILE]
+
+  .. include:: ../qemu-option-trace.rst.inc
+
+.. option:: -u, --user=USER
+
+  user to drop privileges to
+
+.. option:: -g, --group=GROUP
+
+  group to drop privileges to
+
+.. option:: -h, --help
+
+  Display a help message and exit.
+
+.. option:: -V, --version
+
+  Display version information and exit.