[Qemu-devel] [PATCH] virtio-blk: Allow startup of empty cdroms

[Michal Privoznik]

If you have an empty IDE cdrom we will start just fine:

-drive if=none,id=drive-ide0-0-0,readonly=on
-device ide-cd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0

However, that's not the case with virtio disk:

-drive if=none,media=cdrom,id=drive-virtio-disk1,readonly=on
-device 
virtio-blk-pci,scsi=off,bus=pci.2,addr=0x2,drive=drive-virtio-disk1,id=virtio-disk1

One will get the following error:

qemu-system-x86_64: -device 
virtio-blk-pci,scsi=off,bus=pci.2,addr=0x2,drive=drive-virtio-disk1,id=virtio-disk1:
 Device needs media, but drive is empty

The error comes from virtio_blk_device_realize() where we check
if virtio block device has a media inserted. This should,
however, be not required for cdroms.

Signed-off-by: Michal Privoznik <address@hidden>
---
 hw/block/virtio-blk.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 51f867b..2f687d2 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -893,6 +893,7 @@ static void virtio_blk_device_realize(DeviceState *dev, 
Error **errp)
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
     VirtIOBlock *s = VIRTIO_BLK(dev);
     VirtIOBlkConf *conf = &s->conf;
+    DriveInfo *dinfo;
     Error *err = NULL;
     static int virtio_blk_id;
 
@@ -900,7 +901,10 @@ static void virtio_blk_device_realize(DeviceState *dev, 
Error **errp)
         error_setg(errp, "drive property not set");
         return;
     }
-    if (!blk_is_inserted(conf->conf.blk)) {
+
+    dinfo = blk_legacy_dinfo(conf->conf.blk);
+    if (!((dinfo && dinfo->media_cd) ||
+          blk_is_inserted(conf->conf.blk))) {
         error_setg(errp, "Device needs media, but drive is empty");
         return;
     }
-- 
2.4.10