qemu: domain: Store whether a virStorageSource is a host CDROM drive

Use virFileIsCDROM to detect whether a block device is a cdrom drive and
store it in virStorageSource. This will be necessary to correctly create
the 'host_cdrom' backend in qemu when using -blockdev.

We assume that host_cdrom makes only sense when used directly as a raw
image, but if a backing chain would be put in front of it, libvirt will
use 'host_device' in that case.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>

src/qemu/qemu_domain.c

@@ -7530,6 +7530,14 @@ qemuDomainDetermineDiskChain(virQEMUDriverPtr driver,
             VIR_ALLOC(src->backingStore) < 0)
             goto cleanup;
 
+        /* host cdrom requires special treatment in qemu, so we need to check
+         * whether a block device is a cdrom */
+        if (disk->device == VIR_DOMAIN_DISK_DEVICE_CDROM &&
+            src->format == VIR_STORAGE_FILE_RAW &&
+            virStorageSourceIsBlockLocal(src) &&
+            virFileIsCDROM(src->path) == 1)
+            src->hostcdrom = true;
+
         ret = 0;
         goto cleanup;
     }

src/util/virstoragefile.h

@@ -316,6 +316,8 @@ struct _virStorageSource {
 
     bool floppyimg; /* set to true if the storage source is going to be used
                        as a source for floppy drive */
+
+    bool hostcdrom; /* backing device is a cdrom */
 };