Re: [Qemu-devel] [Qemu-ppc] [QEMU-PPC] [PATCH V3 0/6] target/ppc: Rework spapr_caps

[Alexey Kardashevskiy <aik@ozlabs.ru>]

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On 17/01/18 09:34, David Gibson wrote:
> On Tue, Jan 16, 2018 at 03:46:20PM +0100, Andrea Bolognani wrote:
>> On Wed, 2018-01-17 at 00:54 +1100, David Gibson wrote:
>>>> Correct me if I'm wrong, but it seems to me like there's no way
>>>> to figure out through QMP whether these new machine options can be
>>>> used for a given QEMU binary.
>>>
>>> Uh, I don't think so.  These are machine options like any other (just
>>> constructed a bit differently).  So they'll appear in qemu -machine
>>> pseries,? and I believe that info can also be retrieved with QMP.
>>
>> Yes, they will indeed show up in the output of -machine pseries,?
>> but there's AFAICT no way to retrieve them via QMP.
> 
> Really!?  I thought introspecting object properties was QMP's bread
> and butter.


On a guest started with '-S':
{"execute": "qom-list", "arguments": {"path": "/machine"}}

returns:
{   'return': [   {'name': 'graphics', 'type': 'bool'},
                  {'name': 'phandle-start', 'type': 'int'},
                  {'name': 'dump-guest-core', 'type': 'bool'},
                  {'name': 'kernel-irqchip', 'type': 'OnOffSplit'},
                  {'name': 'accel', 'type': 'string'},
                  {'name': 'append', 'type': 'string'},
                  {'name': 'dumpdtb', 'type': 'string'},
                  {'name': 'igd-passthru', 'type': 'bool'},
                  {'name': 'dt-compatible', 'type': 'string'},
                  {'name': 'kernel', 'type': 'string'},
                  {'name': 'usb', 'type': 'bool'},
                  {'name': 'suppress-vmdesc', 'type': 'bool'},
                  {'name': 'dtb', 'type': 'string'},
                  {'name': 'firmware', 'type': 'string'},
                  {'name': 'mem-merge', 'type': 'bool'},
                  {'name': 'initrd', 'type': 'string'},
                  {'name': 'enforce-config-section', 'type': 'bool'},
                  {'name': 'kvm-shadow-mem', 'type': 'int'},
                  {'name': 'cap-dfp', 'type': 'bool'},
                  {'name': 'cap-htm', 'type': 'bool'},
                  {'name': 'cap-vsx', 'type': 'bool'},
                  {'name': 'vfio-no-msix-emulation', 'type': 'bool'},
                  {'name': 'kvm-type', 'type': 'string'},
                  {'name': 'max-cpu-compat', 'type': 'string'},
                  {   'name': 'dr-connector[268435480]',
                      'type': 'child<spapr-drc-cpu>'},
                  {'name': 'peripheral', 'type': 'child<container>'},
                  {   'name': 'dr-connector[268435472]',
                      'type': 'child<spapr-drc-cpu>'},
                  {'name': 'modern-hotplug-events', 'type': 'bool'},
                  {   'name': 'dr-connector[268435464]',
                      'type': 'child<spapr-drc-cpu>'},
                  {   'name': 'dr-connector[268435456]',
                      'type': 'child<spapr-drc-cpu>'},
                  {'name': 'peripheral-anon', 'type': 'child<container>'},
                  {'name': 'ics', 'type': 'child<icskvm>'},
                  {'name': 'vsmt', 'type': 'uint32'},
                  {'name': 'type', 'type': 'string'},
                  {'name': 'rtc-time', 'type': 'struct tm'},
                  {'name': 'unattached', 'type': 'child<container>'},
                  {'name': 'rtc', 'type': 'child<spapr-rtc>'},
                  {'name': 'resize-hpt', 'type': 'string'}]}


but still requires a running qemu, yes.

> 
>> And libvirt
>> can't afford to spawn a QEMU process for each machine type
>> implemented by each QEMU binary installed on the system just to
>> figure out what properties they support; in fact, we've been
>> pushing away from that approach - which was used initially - for
>> years and we're now at the point where we only fall back to it
>> for positively ancient QEMU versions. So the information needs
>> to be available through QMP for libvirt to consume it.
> 
> Right, I'm not arguing with that.  It's just that I thought that
> standard QOM properties on QOM objects (the machine in this case) met
> the criteria.
> 


-- 
Alexey


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