Re: [Qemu-devel] [PATCH RFC 1/1] arm64: add an option to turn on/off vpmu support

[Andrea Bolognani]

On Mon, 2016-08-01 at 15:08 +0200, Andrew Jones wrote:
> > I'm not sure a warning is enough: if I start a guest and
> > explicitly ask for a PMU, I expect it to be there, or for
> > the guest not to start at all. How does x86 behave in this
> > regard?
> 
> Peter had a good suggestion for this. We need to wrap the property
> addition in an arm_feature check like the has_el3 property. That will
> remove it from all cpu types that don't support it.

Wouldn't that mean that you'd be unable to use

  -cpu foo,pmu=off

if CPU model 'foo' doesn't support a PMU? I'd expect that
to work.

I've played around with this a bit on x86 and it doesn't
look like it necessarily behaves the way I'd expect it to,
either, so maybe this is just a case of my expectations
being unreasonable? :)

-- 
Andrea Bolognani / Red Hat / Virtualization