[libvirt] [PATCH 3/4] qemu: monitor: Add vcpu state information to monitor data

[Dou Liyang]

At 09/14/2016 11:35 AM, Peter Krempa wrote:
> On Wed, Sep 14, 2016 at 10:26:51 +0800, Dou Liyang wrote:
>> Hi Peter,
>>
>> At 09/14/2016 12:27 AM, Peter Krempa wrote:
>>> Return whether a vcpu entry is hotpluggable or online so that upper
>>> layers don't have to infer the information from other data.
>>>
>>> Advantage is that this code can be tested by unit tests.
>>> ---
>>>  src/qemu/qemu_monitor.c                            | 11 +++++
>>>  src/qemu/qemu_monitor.h                            |  4 ++
>>>  .../qemumonitorjson-cpuinfo-ppc64-basic.data       | 48 ++++++++++++++++++++++
>>>  .../qemumonitorjson-cpuinfo-ppc64-hotplug-1.data   | 48 ++++++++++++++++++++++
>>>  .../qemumonitorjson-cpuinfo-ppc64-hotplug-2.data   | 48 ++++++++++++++++++++++
>>>  .../qemumonitorjson-cpuinfo-ppc64-hotplug-4.data   | 48 ++++++++++++++++++++++
>>>  .../qemumonitorjson-cpuinfo-ppc64-no-threads.data  | 32 +++++++++++++++
>>>  ...emumonitorjson-cpuinfo-x86-basic-pluggable.data | 16 ++++++++
>>>  .../qemumonitorjson-cpuinfo-x86-full.data          | 22 ++++++++++
>>>  tests/qemumonitorjsontest.c                        |  3 ++
>>>  10 files changed, 280 insertions(+)
>>>
>>> diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
>>> index 4489997..e700b15 100644
>>> --- a/src/qemu/qemu_monitor.c
>>> +++ b/src/qemu/qemu_monitor.c
>>> @@ -1773,6 +1773,7 @@ qemuMonitorGetCPUInfoHotplug(struct qemuMonitorQueryHotpluggableCpusEntry *hotpl
>>>      int order = 1;
>>>      size_t totalvcpus = 0;
>>>      size_t mastervcpu; /* this iterator is used for iterating hotpluggable entities */
>>> +    size_t slavevcpu; /* this corresponds to subentries of a hotpluggable entry */
>>>      size_t anyvcpu; /* this iterator is used for any vcpu entry in the result */
>>>      size_t i;
>>>      size_t j;
>>> @@ -1816,6 +1817,10 @@ qemuMonitorGetCPUInfoHotplug(struct qemuMonitorQueryHotpluggableCpusEntry *hotpl
>>>       * logical vcpus in the guest */
>>>      mastervcpu = 0;
>>>      for (i = 0; i < nhotplugvcpus; i++) {
>>> +        vcpus[mastervcpu].online = !!hotplugvcpus[i].qom_path;
>>> +        vcpus[mastervcpu].hotpluggable = !!hotplugvcpus[i].alias;
>>> +        if (!vcpus[mastervcpu].online)
>>> +            vcpus[mastervcpu].hotpluggable = true;
>>
>> I think if the vcpu don't have an alias, we mark it as non-hotpluggable.
>> so, the code above may not fit well.
>
> The hotplugvcpus.alias field is NULL in the following two cases:
> 1) vcpu is online but was selected as non-hotpluggable
> 2) the vcpu is offline
>

Yes, I see. I confused it with the id feature in QEmu device_add 
command. Sorry for trouble you.

By the way, as far as I know, the online/offline usually refer to the 
status of a CPU. Before we use the status, the CPU has already existed.
Here, we use the online/offline to represent qom_path which indicates
that the CPU is existed or not.
So, it causes me do that judgment. :)

Thanks,
Dou

> The hotpluggable field in libvirt is covering both the hotplug and
> hotunplug case, thus a vcpu shall be marked as hotpluggable if:
>
> 1) it's offline
> 2) has the correct alias.
>
>> I guess you may mean that:
>>
>> vcpus[mastervcpu].online = !!hotplugvcpus[i].qom_path;
>> vcpus[mastervcpu].hotpluggable = false;
>> if (!vcpus[mastervcpu].online && (!!hotplugvcpus[i].alias))
>>      vcpus[mastervcpu].hotpluggable = true;
>
> This is wrong as online vcpus would not be marked as hotpluggable (which
> by the way in the libvirt context also means that it can be unplugged).
>
>>
>> OR
>>
>> vcpus[mastervcpu].online = !!hotplugvcpus[i].qom_path;
>>
>> if (vcpus[mastervcpu].online)
>>      vcpus[mastervcpu].hotpluggable = false;
>
> This is wrong in the same regards.
>
>> else
>>      vcpus[mastervcpu].hotpluggable = !!hotplugvcpus[i].alias;
>
> Also offline vcpu won't ever have an alias, since it's offline.
>
> Peter
>
>