Re: [Qemu-devel] [PATCH v3 5/7] hmp: Add info commands for preconfig

[Markus Armbruster <armbru@redhat.com>]

"Dr. David Alan Gilbert" <dgilbert@redhat.com> writes:

> * Markus Armbruster (armbru@redhat.com) wrote:
>> "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> writes:
>> 
>> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>> >
>> > Allow a bunch of the info commands to be used in preconfig.
>> >
>> > version, chardev, name, uuid,memdev, iothreads
>> >   Were enabled in QMP in the previous patch from Igor
>> 
>> Yes, these are okay together with PATCH 4.
>> 
>> > status, hotpluggable_cpus
>> >   Was enabled in the original allow-preconfig series
>> 
>> query-status looks okay to me.
>> 
>> > history
>> >   is HMP specific
>> 
>> Yes.
>> 
>> > usbhost, qom-tree, numa
>> >   Don't have a QMP equivalent
>> 
>> HMP commands without a QMP equivalent are okay if their functionality
>> makes no sense in QMP, or is of use only for human users.
>> 
>> Example for "makes no sense in QMP": setting the current CPU, because a
>> QMP monitor doesn't have a current CPU.
>> 
>> Examples for "is of use only for human users": HMP command "help", the
>> integrated pocket calculator.
>
> Right, but they do already exist; it's possible we may want to fix/add
> QMP versions - but this series isn't about going through and fixing
> existing stuff up.
>
>> Now let's review the three commands:
>> 
>> * Gerd, why does "info usbhost" have no QMP equivalent?
>> 
>> * Eduardo, why does "info numa" have no QMP equivalent?
>> 
>> * "info qom-tree" is a recursive variant of qom-list that skips anything
>>   but children.  This convenience command exists so you don't have to
>>   filter and string together output from many qom-list.
>> 
>>   I think it stands to reason that if providing "info qom-tree" makes
>>   sense, then so does qom-list (HMP and QMP).  If qom-list, then
>>   qom-list-types, qom-list-properties, qom-get, and probably even
>>   qom-set (I've always been suspicious of qom-set, but that has nothing
>>   to do with preconfig state).
>> 
>>   It might make sense to split off the whole QOM shebang into a separate
>>   patch.
>
> People have been trying to add qom-get etc for quite a while (I tried a
> couple of years ago); it gets stuck in type display issues.  I've not
> directly seen a need for those other variants, but qom-get is something
> I'd love to have, still that's a job for another patch.

Yes.

> 'info qom-tree' is very very useful when debugging qemu to see what the
> basic state we're building is; it's primarily for debugging.

I'm not at all opposed to enabling qom-tree, but I want its QMP building
blocks enabled as well then.  I think enabling their HMP buddies as well
would only make sense.