
In QEMU 1.6 parameters of 'drive' option were removed: QemuOptsList qemu_drive_opts = { .name = "drive", .head = QTAILQ_HEAD_INITIALIZER(qemu_drive_opts.head), .desc = { /* * no elements => accept any params * validation will happen later */ { /* end of list */ } }, }; But libvirt still checks for QEMU_CAPS_DRIVE_DISCARD using QMP query-command-line-options: static struct virQEMUCapsCommandLineProps virQEMUCapsCommandLine[] = { { "machine", "mem-merge", QEMU_CAPS_MEM_MERGE }, { "drive", "discard", QEMU_CAPS_DRIVE_DISCARD }, { "realtime", "mlock", QEMU_CAPS_MLOCK }, }; ... qemuMonitorGetCommandLineOptionParameters(mon, virQEMUCapsCommandLine[i].option, &values) So, when I try to use discard option in domain xml I get this error: error : qemuBuildDriveStr:3986 : unsupported configuration: discard is not supported by this QEMU binary