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

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 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",
+            .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}).
 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.
+ item fd= var{fd}
+This option defines which disk image (@pxref{disk_images}) file descriptor to
+use with this drive.
+ 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:
+ example
+qemu-system-i386 -drive fd=24,opaque="rdwr:/path/to/file",index=0,media=disk
+ end example
 You can connect a CDROM to the slave of ide0:
 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:
 qemu-system-i386 -drive if=ide,index=1,media=cdrom
 @end example

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