Red Hat Bugzilla – Bug 1263978
qmp don't support {"execute":"qom-get","arguments":{"path":"/machine","property":"rtc-time"}}
Last modified: 2016-09-20 00:41:30 EDT
Description of problem: qmp don't support {"execute":"qom-get","arguments":{"path":"/machine","property":"rtc-time"}} Version-Release number of selected component (if applicable): Host: 3.10.0-315.el7.x86_64 qemu-kvm-1.5.3-103.el7 How reproducible: 100% Steps to Reproduce: 1.Start qemu-kvm process, execute qom-get. # /usr/libexec/qemu-kvm -qmp tcp:0:6773,server,nowait {"QMP": {"version": {"qemu": {"micro": 3, "minor": 5, "major": 1}, "package": " (qemu-kvm-1.5.3-103.el7)"}, "capabilities": []}} { "execute": "qmp_capabilities" } {"return": {}} {"execute":"qom-get","arguments":{"path":"/machine","property":"rtc-time"} } {"error": {"class": "GenericError", "desc": "Property '.rtc-time' not found"}} 2. 3. Actual results: Not found rtc-time. Expected results: qemu-kvm also support rtc-time. Additional info: qemu-kvm-rhev-2.3.0-23.el7 works well. {"QMP": {"version": {"qemu": {"micro": 0, "minor": 3, "major": 2}, "package": " (qemu-kvm-rhev-2.3.0-23.el7)"}, "capabilities": []}} { "execute": "qmp_capabilities" } {"return": {}} {"execute":"qom-get","arguments":{"path":"/machine","property":"rtc-time"} } {"return": {"tm_year": 115, "tm_sec": 48, "tm_hour": 8, "tm_min": 50, "tm_mon": 8, "tm_mday": 17}}
"/machine/rtc-time" is an alias to the property of the actual RTC device. Added upstream in commit 654a36d, v2.1.0. Not in RHEL-7 qemu-kvm. For PC machines, the RTC device is "mc146818rtc", and "/machine/rtc-time" is an alias for "/machine/unattached/device[X]/date", where X can vary between versions. In my build of RHEL-6's qemu-kvm, it's 7. To find the "mc146818rtc" device, search for the device with type "mc146818rtc", like this: QMP> { "execute": "qom-get", "arguments": { "path": "/machine/unattached/device[1]", "property": "type" } } {"return": "kvmvapic"} Not the right one, try next QMP> { "execute": "qom-get", "arguments": { "path": "/machine/unattached/device[2]", "property": "type" } } {"return": "kvmclock"} and so forth until QMP> { "execute": "qom-get", "arguments": { "path": "/machine/unattached/device[7]", "property": "type" } } {"return": "mc146818rtc"} QMP> { "execute": "qom-get", "arguments": { "path": "/machine/unattached/device[7]", "property": "date" } } {"return": {"tm_year": 115, "tm_sec": 31, "tm_hour": 17, "tm_min": 27, "tm_mon": 8, "tm_mday": 18}} The stable alias saves you from having to know the machine's RTC device and the name of its property (neither is going to change in RHEL-7 qemu-kvm), and saves you the search for it. If you think we should backport the "/machine/rtc-time" alias to RHEL-7 qemu-kvm, please state your business case. If not, let us know so we can close out this bug.
This bug is according to qe's test case, I'll talk with the feature owner if close it. Since he is on pto, I'll update this bug when he back. Thanks, Mazhang.
Just talk to scui, not need backport to qemu-kvm, so close this bug. Thanks, Mazhang.