Re: [PATCH 092/104] virtiofsd: add man page

["Daniel P. Berrangé" <berrange@redhat.com>]

On Thu, Dec 12, 2019 at 04:38:52PM +0000, Dr. David Alan Gilbert (git) wrote:
> From: Stefan Hajnoczi <stefanha@redhat.com>
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  Makefile                       |  7 +++
>  tools/virtiofsd/virtiofsd.texi | 85 ++++++++++++++++++++++++++++++++++
>  2 files changed, 92 insertions(+)
>  create mode 100644 tools/virtiofsd/virtiofsd.texi

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

with some notes at the very end


> diff --git a/Makefile b/Makefile
> index fa15174ba0..53d175d12f 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -357,6 +357,9 @@ DOCS+=docs/qemu-cpu-models.7
>  ifdef CONFIG_VIRTFS
>  DOCS+=fsdev/virtfs-proxy-helper.1
>  endif
> +ifdef CONFIG_LINUX
> +DOCS+=tools/virtiofsd/virtiofsd.1
> +endif
>  ifdef CONFIG_TRACE_SYSTEMTAP
>  DOCS+=scripts/qemu-trace-stap.1
>  endif
> @@ -863,6 +866,9 @@ ifdef CONFIG_VIRTFS
>  	$(INSTALL_DIR) "$(DESTDIR)$(mandir)/man1"
>  	$(INSTALL_DATA) fsdev/virtfs-proxy-helper.1 "$(DESTDIR)$(mandir)/man1"
>  endif
> +ifdef CONFIG_LINUX
> +	$(INSTALL_DATA) tools/virtiofsd/virtiofsd.1 "$(DESTDIR)$(mandir)/man1"
> +endif
>  
>  install-datadir:
>  	$(INSTALL_DIR) "$(DESTDIR)$(qemu_datadir)"
> @@ -1061,6 +1067,7 @@ qemu.1: qemu-doc.texi qemu-options.texi qemu-monitor.texi qemu-monitor-info.texi
>  qemu.1: qemu-option-trace.texi
>  qemu-img.1: qemu-img.texi qemu-option-trace.texi qemu-img-cmds.texi
>  fsdev/virtfs-proxy-helper.1: fsdev/virtfs-proxy-helper.texi
> +tools/virtiofsd/virtiofsd.1: tools/virtiofsd/virtiofsd.texi
>  qemu-nbd.8: qemu-nbd.texi qemu-option-trace.texi
>  docs/qemu-block-drivers.7: docs/qemu-block-drivers.texi
>  docs/qemu-cpu-models.7: docs/qemu-cpu-models.texi
> diff --git a/tools/virtiofsd/virtiofsd.texi b/tools/virtiofsd/virtiofsd.texi
> new file mode 100644
> index 0000000000..eec7fbf4e6
> --- /dev/null
> +++ b/tools/virtiofsd/virtiofsd.texi
> @@ -0,0 +1,85 @@
> +@example
> +@c man begin SYNOPSIS
> +@command{virtiofsd} [OPTION] @option{--socket-path=}@var{path}|@option{--fd=}@var{fdnum} @option{-o source=}@var{path}
> +@c man end
> +@end example
> +
> +@c man begin 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 @code{--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.

So there's no way for an unprivileged user to do file sharing like they
can with 9p right now ?

>                                              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.
> +
> +@c man end
> +
> +@c man begin OPTIONS
> +@table @option
> +@item -h, --help
> +Print help.
> +@item -V, --version
> +Print version.
> +@item -d, -o debug
> +Enable debug output.
> +@item --syslog
> +Print log messages to syslog instead of stderr.
> +@item -o log_level=@var{level}
> +Print only log messages matching @var{level} or more severe.  @var{level} is
> +one of @code{err}, @code{warn}, @code{info}, or @code{debug}.  The default is
> +@var{info}.
> +@item -o source=@var{path}
> +Share host directory tree located at @var{path}.  This option is required.
> +@item --socket-path=@var{path}, -o vhost_user_socket=@var{path}
> +Listen on vhost-user UNIX domain socket at @var{path}.
> +@item --fd=@var{fdnum}
> +Accept connections from vhost-user UNIX domain socket file descriptor @var{fdnum}.  The file descriptor must already be listening for connections.
> +@item --thread-pool-size=@var{num}
> +Restrict the number of worker threads per request queue to @var{num}.  The default is 64.
> +@item --cache=@code{none}|@code{auto}|@code{always}
> +Select the desired trade-off between coherency and performance.  @code{none}
> +forbids the FUSE client from caching to achieve best coherency at the cost of
> +performance.  @code{auto} acts similar to NFS with a 1 second metadata cache
> +timeout.  @code{always} sets a long cache lifetime at the expense of coherency.
> +@item --writeback
> +Enable writeback cache, allowing the FUSE client to buffer and merge write requests.
> +@end table
> +@c man end
> +
> +@c man begin EXAMPLES
> +Export @code{/var/lib/fs/vm001/} on vhost-user UNIX domain socket @code{/var/run/vm001-vhost-fs.sock}:
> +
> +@example
> +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-file,id=mem,size=4G,mem-path=/dev/shm,share=on \
> +    -numa node,memdev=mem \
> +    ...
> +guest# mount -t virtio_fs \
> +    -o default_permissions,allow_other,user_id=0,group_id=0,rootmode=040000,dax \
> +    myfs /mnt
> +@end example
> +@c man end
> +
> +@ignore
> +@setfilename virtiofsd
> +@settitle QEMU virtio-fs shared file system daemon
> +
> +@c man begin AUTHOR

s/AUTHOR/COPYRIGHT/

since this isn't providing any author information.

> +Copyright (C) 2019 Red Hat, Inc.

2019-2020 !

And now insert

 @c man end
 @c man begin LICENSE

> +This is free software; see the source for copying conditions.  There is NO
> +warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> +@c man end
> +@end ignore



Regards,
Daniel
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