[libvirt] [Qemu-devel] [PATCH 3/4] qemu-config: Add -drive fd and opaque options

[Blue Swirl]

On Fri, Oct 5, 2012 at 6:07 PM, Corey Bryant <coreyb at linux.vnet.ibm.com> wrote:
> These new options can be used for passing drive file descriptors
> on the command line, instead of using the file option to specify
> a file name.
>
> These new command line options mirror the existing add-fd QMP
> command which allows an fd to be passed to QEMU via SCM_RIGHTS and
> added to an fd set.  The opaque option is also available with
> add-fd, and allows a free-form string to be stored in the fd set
> along with the fd.
>
> Signed-off-by: Corey Bryant <coreyb at linux.vnet.ibm.com>
> ---
>  qemu-config.c   |  8 ++++++++
>  qemu-options.hx | 15 +++++++++++++--
>  2 files changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/qemu-config.c b/qemu-config.c
> index cd1ec21..91053dd 100644
> --- a/qemu-config.c
> +++ b/qemu-config.c
> @@ -114,6 +114,14 @@ static QemuOptsList qemu_drive_opts = {
>              .name = "copy-on-read",
>              .type = QEMU_OPT_BOOL,
>              .help = "copy read data from backing file into image file",
> +        },{
> +            .name = "fd",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "disk image file descriptor",
> +        },{
> +            .name = "opaque",

'opaque' is not very descriptive and it's also not obvious (except
from the help text) that it's only interesting for file descriptors.
How about fd_name, fd_tag or fd_descr?

> +            .type = QEMU_OPT_STRING,
> +            .help = "free-form string used to describe fd",
>          },
>          { /* end of list */ }
>      },
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 7d97f96..513530f 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -149,7 +149,7 @@ using @file{/dev/cdrom} as filename (@pxref{host_drives}).
>  ETEXI
>
>  DEF("drive", HAS_ARG, QEMU_OPTION_drive,
> -    "-drive [file=file][,if=type][,bus=n][,unit=m][,media=d][,index=i]\n"
> +    "-drive [file=file|fd=fd[,opaque=o]][,if=type][,bus=n][,unit=m][,media=d][,index=i]\n"
>      "       [,cyls=c,heads=h,secs=s[,trans=t]][,snapshot=on|off]\n"
>      "       [,cache=writethrough|writeback|none|directsync|unsafe][,format=f]\n"
>      "       [,serial=s][,addr=A][,id=name][,aio=threads|native]\n"
> @@ -170,6 +170,12 @@ this drive. If the filename contains comma, you must double it
>
>  Special files such as iSCSI devices can be specified using protocol
>  specific URLs. See the section for "Device URL Syntax" for more information.
> + at item fd=@var{fd}
> +This option defines which disk image (@pxref{disk_images}) file descriptor to
> +use with this drive.
> + at item opaque=@var{opaque}
> +This option defines a free-form string that describes @var{fd}.  This is used
> +when storing @var{fd} in a file descriptor set.
>  @item if=@var{interface}
>  This option defines on which type on interface the drive is connected.
>  Available types are: ide, scsi, sd, mtd, floppy, pflash, virtio.
> @@ -257,12 +263,17 @@ qemu-system-i386 -drive file=file,index=2,media=disk
>  qemu-system-i386 -drive file=file,index=3,media=disk
>  @end example
>
> +You can open an image using a pre-opened file descriptor:
> + at example
> +qemu-system-i386 -drive fd=24,opaque="rdwr:/path/to/file",index=0,media=disk
> + at end example
> +
>  You can connect a CDROM to the slave of ide0:
>  @example
>  qemu-system-i386 -drive file=file,if=ide,index=1,media=cdrom
>  @end example
>
> -If you don't specify the "file=" argument, you define an empty drive:
> +If you don't specify the "file=" or "fd=" arguments, you define an empty drive:
>  @example
>  qemu-system-i386 -drive if=ide,index=1,media=cdrom
>  @end example
> --
> 1.7.11.4
>
>