qemu: hotplug: Add warning regarding SD hotplug

SD card hotplug should not be implemented until they can be used via
-blockdev.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

src/qemu/qemu_hotplug.c

@@ -725,6 +725,9 @@ qemuDomainAttachDeviceDiskLive(virQEMUDriverPtr driver,
         case VIR_DOMAIN_DISK_BUS_UML:
         case VIR_DOMAIN_DISK_BUS_SATA:
         case VIR_DOMAIN_DISK_BUS_SD:
+            /* Note that SD card hotplug support should be added only once
+             * they support '-device' (don't require -drive only).
+             * See also: qemuDiskBusNeedsDriveArg */
         case VIR_DOMAIN_DISK_BUS_LAST:
             virReportError(VIR_ERR_OPERATION_UNSUPPORTED,
                            _("disk bus '%s' cannot be hotplugged."),