[xen staging-4.15] libxl: Use -device for cd-rom drives

[patchbot@xxxxxxx]

commit 6165dcfe7e5283c7776f3f40cc905f29ed39486c
Author:     Anthony PERARD <anthony.perard@xxxxxxxxxx>
AuthorDate: Tue May 11 10:28:06 2021 +0100
Commit:     Ian Jackson <iwj@xxxxxxxxxxxxxx>
CommitDate: Thu Aug 19 17:18:07 2021 +0100

    libxl: Use -device for cd-rom drives
    
    This allows to set an `id` on the device instead of only the drive. We
    are going to need the `id` with the "eject" and
    "blockdev-change-media" QMP command as using `device` parameter on
    those is deprecated. (`device` is the `id` of the `-drive` on the
    command line).
    
    We set the same `id` on both -device and -drive as QEMU doesn't
    complain and we can then either do "eject id=$id" or "eject
    device=$id".
    
    Using "-drive + -device" instead of only "-drive" has been
    available since at least QEMU 0.15, and seems to be the preferred way as it
    separates the host part (-drive which describe the disk image location
    and format) from the guest part (-device which describe the emulated
    device). More information in qemu.git/docs/qdev-device-use.txt .
    
    Changing the command line during migration for the cdrom seems fine.
    Also the documentation about migration in QEMU explains that the device
    state ID is "been formed from a bus name and device address", so
    second IDE bus and first device address on bus is still thus and
    doesn't matter if written "-drive if=ide,index=2" or "-drive
    ide-cd,bus=ide.1,unit=0".
    See qemu.git/docs/devel/migration.rst .
    
    Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
    Reviewed-by: Jason Andryuk <jandryuk@xxxxxxxxx>
    
    Backport-requested-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
    Acked-by: Ian Jackson <iwj@xxxxxxxxxxxxxx>
---
 tools/libs/light/libxl_dm.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/tools/libs/light/libxl_dm.c b/tools/libs/light/libxl_dm.c
index 21fe33d3e2..1e16f9e5b6 100644
--- a/tools/libs/light/libxl_dm.c
+++ b/tools/libs/light/libxl_dm.c
@@ -1913,6 +1913,7 @@ static int libxl__build_device_model_args_new(libxl__gc 
*gc,
             }
 
             if (disks[i].is_cdrom) {
+                const char *drive_id;
                 if (disk > 4) {
                     LOGD(WARN, guest_domid, "Emulated CDROM can be only one of 
the first 4 disks.\n"
                          "Disk %s will be available via PV drivers but not as 
an "
@@ -1920,13 +1921,22 @@ static int libxl__build_device_model_args_new(libxl__gc 
*gc,
                          disks[i].vdev);
                     continue;
                 }
-                drive = libxl__sprintf(gc,
-                         "if=ide,index=%d,readonly=on,media=cdrom,id=ide-%i",
-                         disk, dev_number);
+
+                drive_id = GCSPRINTF("ide-%i", dev_number);
+                drive = GCSPRINTF("if=none,readonly=on,id=%s", drive_id);
 
                 if (target_path)
                     drive = libxl__sprintf(gc, "%s,file=%s,format=%s",
                                            drive, target_path, format);
+
+                flexarray_vappend(dm_args,
+                    "-drive", drive,
+                    "-device",
+                    GCSPRINTF("ide-cd,id=%s,drive=%s,bus=ide.%u,unit=%u",
+                              drive_id, drive_id,
+                              disk / 2, disk % 2),
+                    NULL);
+                continue;
             } else {
                 /*
                  * Explicit sd disks are passed through as is.
--
generated by git-patchbot for /home/xen/git/xen.git#staging-4.15