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

[Dave Martin]

On Wed, May 15, 2019 at 09:18:54AM +0100, Andrew Jones wrote:
> On Tue, May 14, 2019 at 04:48:38PM +0200, Igor Mammedov wrote:
> > On Tue, 14 May 2019 11:02:25 +0200
> > Andrew Jones <address@hidden> wrote:
> > > My thought is primarily machines. If a human wants to use the command
> > > line and SVE, then I'm assuming they'll be happy with sve-max-vq or
> > > figuring out a map they like once and then sticking to it.
> > 
> > maybe naive question, but why not use a property/bit as user facing 
> > interface,
> > in line with what we do with CPUID bits. (that's assuming that bits have
> > fixed meaning).
> > Yes, it's verbose but follows current practice and works fine with -cpu and
> > -device.
> > (I really hate custom preprocessing of -cpu and we were working hard to 
> > remove
> > that in favor of canonical properties at the expense of more verbose CLI).
> >
> 
> Are you asking if we should do something like the following?
> 
>   -cpu host,sve1=on,sve=2=on,sve3=off,sve4=on

Note, there is nothing SVE-specific about this.

Either enabling features on a per-vcpu basis is justified, or it isn't:
if it's justified, then it would be better to have a general way of
specifying per-vcpu properties, rather than it being reinvented per
feature.

Creating mismatched configurations is allowed by the architecture and so
it's useful for testing the kernel, but probably less useful for real-
world use cases today.

So it may be a good idea to get the symmetric support sorted out first
before thinking about whether and how to specify asymmetric
configurations.

Cheers
---Dave