Daniel P. Berrangé <berra...@redhat.com> writes:
> On Thu, Feb 06, 2020 at 10:40:37AM +0100, Markus Armbruster wrote:
>> > If the user screwsup, it should give an error that prompts the user
>> > to the parameter they got wrong.
>> >
>> > Output from commands should normally be pretty formatted (with an option
>> > to display raw json for those needing it).
>> > e.g. that 'query-version' should give either just the package
>> > version (as info version currently does) or:
>> > 4.2.50 Package: v4.2.0-1188-gd95a3885a9
>> >
>> > We shouldn't lose any HMP commands that some people find useful
>> > Ditching HMP isn't an option until we've got almost all of it
>> > covered.
>>
>> In particular, we currently use HMP for debugging and monitoring
>> purposes, where we don't need or want QMP's rigor, neither its rigorous
>> interface stability, nor its structured I/O. We want the "whipuptitude"
>> we get from monitor_printf(). This is actually a point David has made
>> several times.
>
> I'd like to argue that this decision to keep these debugging/monitoring
> things in HMP only was a mistake, because it ensures that QEMU internals
> need to keep HMP related code forever.
>
> What we actually need is a part of QMP that does not have the long term
> stability requirement, nor need for fully structured data. In fact this
> pretty much already exists - we have declared the 'x-' prefix as a way
> to model QMP commands which are experimental / suboptimal / subject
> to change.
>
> I suggest that every HMP command which does not have a QMP equivalent
> should be turned into a QMP command with an "x-" prefix, with no
> extra modelling applied
Makes sense (see my point about "allowing some [whipuptitude] in QMP"),
except I disagree with your example:
> Take "info block"
>
> (hmp) info block
> ide1-cd0: [not inserted]
> Attached to: /machine/unattached/device[23]
> Removable device: not locked, tray closed
>
> floppy0: [not inserted]
> Attached to: /machine/unattached/device[16]
> Removable device: not locked, tray closed
>
> sd0: [not inserted]
> Removable device: not locked, tray closed
>
>
> I suggest we support it as "x-query-block"
>
> (qmp) x-query-block
> {
> "return": {
> "info": "ide1-cd0: [not inserted]
> Attached to: /machine/unattached/device[23]
> Removable device: not locked, tray closed
>
> floppy0: [not inserted]
> Attached to: /machine/unattached/device[16]
> Removable device: not locked, tray closed
>
> sd0: [not inserted]
> Removable device: not locked, tray closed"
> }
> }
This commmand does have a QMP equivalent: query-block.
Hmm, no more. It actually wraps around both query-block and
query-named-block-nodes now. I think that makes it an example of "go
beyond 1:1".
A better example for "allowing whipuptitude" would be "info registers".
> Functionally we in fact already support pretty much exactly
> that via the "human-monitor-command" QMP command.
>
> The difference is that with the latter, we will still have to
> keep around the internal dispatching machinery for HMP inside
> QEMU forever. If we transplant all remaining HMP commands with
> an "x-" prefix, we open up the possibility of completely
> separating HMP out and having QEMU work exclusively with QMP
> internally.
>
> This is complementary to an improved qmp-shell client.
Yes.
