Re: [Qemu-devel] How do we do user input bitmap properties?

[Eduardo Habkost]

On Mon, May 27, 2019 at 06:29:44PM +0200, Andrea Bolognani wrote:
> On Fri, 2019-05-24 at 15:24 -0300, Eduardo Habkost wrote:
> > On Thu, May 23, 2019 at 10:35:24AM +0200, Andrea Bolognani wrote:
> > > [...] the above looks good to
> > > me as a general direction, but note that you'll have to implement at
> > > the very least the query-cpu-model-expansion QMP command for the
> > > introspection to work.
> > 
> > Why is query-cpu-model-expansion needed?  Isn't
> > device-list-properties enough?
> 
> Good question.
> 
> I'll have to check with Jirka, but from playing with both commands
> it looks like the latter returns a superset of what the former does,
> so for the purpose of figuring out which vector lengths the QEMU
> binary recognizes it should be good enough; I suspect, however, that
> query-cpu-model-expansion might be (made to be) smarter and for
> example not report vector lengths that the underlying hardware
> doesn't support, which would be valuable for the purpose of user
> friendly error reporting and allowing applications to decide which
> vector lengths to request when creating guests.

Yes, query-cpu-model-expansion returns additional information, so
it depends on what exactly you are looking for.

If you want to know which properties a given QEMU binary supports
in the command-line, `device-list-properties` is supposed to be
enough.  If you need to know which properties can be really
enabled in a given host (based on QEMU+KVM+hardware
capabilities), you'll need `query-cpu-model-expansion model=max`.

-- 
Eduardo