docs: add virtiofsd(1) man page

Document the virtiofsd(1) program and its command-line options.  This
man page is a rST conversion of the original texi documentation that I
wrote.

Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

MAINTAINERS

@@ -1613,6 +1613,7 @@ S: Supported
 F: tools/virtiofsd/*
 F: hw/virtio/vhost-user-fs*
 F: include/hw/virtio/vhost-user-fs.h
+F: docs/interop/virtiofsd.rst
 
 virtio-input
 M: Gerd Hoffmann <kraxel@redhat.com>

Makefile

@@ -348,6 +348,9 @@ DOCS=qemu-doc.html qemu-doc.txt qemu.1
 DOCS+=$(MANUAL_BUILDDIR)/interop/qemu-img.1
 DOCS+=$(MANUAL_BUILDDIR)/interop/qemu-nbd.8
 DOCS+=$(MANUAL_BUILDDIR)/interop/qemu-ga.8
+ifeq ($(CONFIG_LINUX)$(CONFIG_SECCOMP)$(CONFIG_LIBCAP_NG),yyy)
+DOCS+=$(MANUAL_BUILDDIR)/interop/virtiofsd.1
+endif
 DOCS+=$(MANUAL_BUILDDIR)/system/qemu-block-drivers.7
 DOCS+=docs/interop/qemu-qmp-ref.html docs/interop/qemu-qmp-ref.txt docs/interop/qemu-qmp-ref.7
 DOCS+=docs/interop/qemu-ga-ref.html docs/interop/qemu-ga-ref.txt docs/interop/qemu-ga-ref.7
@@ -861,6 +864,9 @@ ifdef CONFIG_VIRTFS
 	$(INSTALL_DIR) "$(DESTDIR)$(mandir)/man1"
 	$(INSTALL_DATA) $(MANUAL_BUILDDIR)/interop/virtfs-proxy-helper.1 "$(DESTDIR)$(mandir)/man1"
 endif
+ifeq ($(CONFIG_LINUX)$(CONFIG_SECCOMP)$(CONFIG_LIBCAP_NG),yyy)
+	$(INSTALL_DATA) docs/interop/virtiofsd.1 "$(DESTDIR)$(mandir)/man1"
+endif
 
 install-datadir:
 	$(INSTALL_DIR) "$(DESTDIR)$(qemu_datadir)"
@@ -1051,7 +1057,8 @@ $(MANUAL_BUILDDIR)/system/index.html: $(call manual-deps,system)
 	$(call build-manual,system,html)
 
 $(call define-manpage-rule,interop,\
-       qemu-ga.8 qemu-img.1 qemu-nbd.8 qemu-trace-stap.1 virtfs-proxy-helper.1,\
+       qemu-ga.8 qemu-img.1 qemu-nbd.8 qemu-trace-stap.1\
+       virtiofsd.1 virtfs-proxy-helper.1,\
        $(SRC_PATH/qemu-img-cmds.hx))
 
 $(call define-manpage-rule,system,qemu-block-drivers.7)

docs/interop/conf.py

@@ -27,5 +27,8 @@ man_pages = [
      [], 1),
     ('virtfs-proxy-helper', 'virtfs-proxy-helper',
      u'QEMU 9p virtfs proxy filesystem helper',
-     ['M. Mohan Kumar'], 1)
+     ['M. Mohan Kumar'], 1),
+    ('virtiofsd', 'virtiofsd', u'QEMU virtio-fs shared file system daemon',
+     ['Stefan Hajnoczi <stefanha@redhat.com>',
+      'Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>'], 1),
 ]

docs/interop/index.rst

@@ -24,3 +24,4 @@ Contents:
    vhost-user
    vhost-user-gpu
    virtfs-proxy-helper
+   virtiofsd

docs/interop/virtiofsd.rst

@@ -0,0 +1,120 @@
+QEMU virtio-fs shared file system daemon
+========================================
+
+Synopsis
+--------
+
+**virtiofsd** [*OPTIONS*]
+
+Description
+-----------
+
+Share a host directory tree with a guest through a virtio-fs device.  This
+program is a vhost-user backend that implements the virtio-fs device.  Each
+virtio-fs device instance requires its own virtiofsd process.
+
+This program is designed to work with QEMU's ``--device vhost-user-fs-pci``
+but should work with any virtual machine monitor (VMM) that supports
+vhost-user.  See the Examples section below.
+
+This program must be run as the root user.  Upon startup the program will
+switch into a new file system namespace with the shared directory tree as its
+root.  This prevents "file system escapes" due to symlinks and other file
+system objects that might lead to files outside the shared directory.  The
+program also sandboxes itself using seccomp(2) to prevent ptrace(2) and other
+vectors that could allow an attacker to compromise the system after gaining
+control of the virtiofsd process.
+
+Options
+-------
+
+.. program:: virtiofsd
+
+.. option:: -h, --help
+
+  Print help.
+
+.. option:: -V, --version
+
+  Print version.
+
+.. option:: -d
+
+  Enable debug output.
+
+.. option:: --syslog
+
+  Print log messages to syslog instead of stderr.
+
+.. option:: -o OPTION
+
+  * debug -
+    Enable debug output.
+
+  * flock|no_flock -
+    Enable/disable flock.  The default is ``no_flock``.
+
+  * log_level=LEVEL -
+    Print only log messages matching LEVEL or more severe.  LEVEL is one of
+    ``err``, ``warn``, ``info``, or ``debug``.  The default is ``info``.
+
+  * norace -
+    Disable racy fallback.  The default is false.
+
+  * posix_lock|no_posix_lock -
+    Enable/disable remote POSIX locks.  The default is ``posix_lock``.
+
+  * readdirplus|no_readdirplus -
+    Enable/disable readdirplus.  The default is ``readdirplus``.
+
+  * source=PATH -
+    Share host directory tree located at PATH.  This option is required.
+
+  * timeout=TIMEOUT -
+    I/O timeout in seconds.  The default depends on cache= option.
+
+  * writeback|no_writeback -
+    Enable/disable writeback cache. The cache alows the FUSE client to buffer
+    and merge write requests.  The default is ``no_writeback``.
+
+  * xattr|no_xattr -
+    Enable/disable extended attributes (xattr) on files and directories.  The
+    default is ``no_xattr``.
+
+.. option:: --socket-path=PATH
+
+  Listen on vhost-user UNIX domain socket at PATH.
+
+.. option:: --fd=FDNUM
+
+  Accept connections from vhost-user UNIX domain socket file descriptor FDNUM.
+  The file descriptor must already be listening for connections.
+
+.. option:: --thread-pool-size=NUM
+
+  Restrict the number of worker threads per request queue to NUM.  The default
+  is 64.
+
+.. option:: --cache=none|auto|always
+
+  Select the desired trade-off between coherency and performance.  ``none``
+  forbids the FUSE client from caching to achieve best coherency at the cost of
+  performance.  ``auto`` acts similar to NFS with a 1 second metadata cache
+  timeout.  ``always`` sets a long cache lifetime at the expense of coherency.
+
+Examples
+--------
+
+Export ``/var/lib/fs/vm001/`` on vhost-user UNIX domain socket
+``/var/run/vm001-vhost-fs.sock``:
+
+::
+
+  host# virtiofsd --socket-path=/var/run/vm001-vhost-fs.sock -o source=/var/lib/fs/vm001
+  host# qemu-system-x86_64 \
+      -chardev socket,id=char0,path=/var/run/vm001-vhost-fs.sock \
+      -device vhost-user-fs-pci,chardev=char0,tag=myfs \
+      -object memory-backend-memfd,id=mem,size=4G,share=on \
+      -numa node,memdev=mem \
+      ...
+  guest# mount -t virtiofs myfs /mnt