qemu: command: Move disk index validation closer to usage

The disk index validation is used only in very specific cases and does
not need to be performed otherwise. Move it out of the global check into
the usage place.

src/qemu/qemu_command.c

@@ -1468,15 +1468,8 @@ qemuBuildDriveSourceStr(virDomainDiskDefPtr disk,
 static int
 qemuBuildDriveStrValidate(virDomainDiskDefPtr disk,
                           virQEMUCapsPtr qemuCaps,
-                          const char *bus,
-                          int idx)
+                          const char *bus)
 {
-    if (idx < 0) {
-        virReportError(VIR_ERR_INTERNAL_ERROR,
-                       _("unsupported disk type '%s'"), disk->dst);
-        return -1;
-    }
-
     switch (disk->bus) {
     case VIR_DOMAIN_DISK_BUS_SCSI:
         if (disk->info.type != VIR_DOMAIN_DEVICE_ADDRESS_TYPE_DRIVE) {
@@ -1638,10 +1631,9 @@ qemuBuildDriveStr(virDomainDiskDefPtr disk,
     const char *bus = virDomainDiskQEMUBusTypeToString(disk->bus);
     const char *trans =
         virDomainDiskGeometryTransTypeToString(disk->geometry.trans);
-    int idx = virDiskNameToIndex(disk->dst);
     bool emitDeviceSyntax = qemuDiskBusNeedsDeviceArg(disk->bus);
 
-    if (qemuBuildDriveStrValidate(disk, qemuCaps, bus, idx) < 0)
+    if (qemuBuildDriveStrValidate(disk, qemuCaps, bus) < 0)
         goto error;
 
     if (qemuBuildDriveSourceStr(disk, cfg, &opt, qemuCaps) < 0)
@@ -1671,6 +1663,13 @@ qemuBuildDriveStr(virDomainDiskDefPtr disk,
         virBufferAsprintf(&opt, ",id=%s", drivealias);
         VIR_FREE(drivealias);
     } else {
+        int idx = virDiskNameToIndex(disk->dst);
+
+        if (idx < 0) {
+            virReportError(VIR_ERR_INTERNAL_ERROR,
+                           _("unsupported disk type '%s'"), disk->dst);
+            goto error;
+        }
         virBufferAsprintf(&opt, ",index=%d", idx);
     }
     if (bootable &&