Re: [PATCH for-6.0 1/6] qapi: Add query-accel command

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Nov 18, 2020 at 12:28:45PM +0100, Kevin Wolf wrote:
> Am 18.11.2020 um 09:36 hat Markus Armbruster geschrieben:
> > >> >>                                       [...]  Even better would be
> > >> >> returning an array of KvmInfo with information on all supported
> > >> >> accelerators at once, rather than making the user call this command once
> > >> >> per name.
> > >> >
> > >> > Maybe.  It would save us the work of answering the question
> > >> > above, but is this (querying information for all accelerators at
> > >> > once) going to be a common use case?
> > >> 
> > >> I recommend to scratch the query-accel parameter, and return information
> > >> on all accelerators in this build of QEMU.  Simple, and consistent with
> > >> similar ad hoc queries.  If a client is interested in just one, fishing
> > >> it out of the list is easy enough.
> > >> 
> > >
> > > Works for me. I'll then leave KvmInfo as is and will introduce AccelInfo
> > > with two fields: name and enabled. enabled will be true only for
> > > currently active accelerator.
> > 
> > Please document that at most on result can have 'enabled': true.
> 
> This doesn't feel right.
> 
> If I understand right, the proposal is to get a result like this:
> 
>     [ { 'name': 'kvm', 'enabled': true },
>       { 'name': 'tcg', 'enabled': false },
>       { 'name': 'xen', 'enabled': false } ]
> 
> The condition that only one field can be enabled would only be in the
> documentation instead of being enforced.
> 
> Instead, consider a response like this:
> 
>     { 'available': [ 'kvm', 'tcg', 'xen' ],
>       'active': 'kvm' }
> 
> This is not only shorter, but also makes sure that only one accelerator
> can be reported as active.

I guess this can be extended with a union to report extra props for the
accelerator, discriminated on the 'active' field eg

     { 'available': [ 'kvm', 'tcg', 'xen' ],
       'active': 'kvm',
       'data': {
           "allow-nested": true,
       }
    }


Regards,
Daniel
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