Re: [Qemu-devel] [RFC PATCH 0/2] ARM: add QMP command to query GIC version

[Andrew Jones <drjones@redhat.com>]

On Mon, Feb 15, 2016 at 08:40:54PM +0100, Markus Armbruster wrote:
> Peter Maydell <peter.maydell@linaro.org> writes:
> 
> > On 15 February 2016 at 15:08, Markus Armbruster <armbru@redhat.com> wrote:
> >> Peter Xu <peterx@redhat.com> writes:
> >>> On Mon, Feb 15, 2016 at 10:52:01AM +0100, Markus Armbruster wrote:
> >>>> Peter Xu <peterx@redhat.com> writes:
> >>>> Adding ad hoc queries as we go won't scale.  Is there really no generic
> >>>> way to get this information, e.g. with qom-get?
> >>>
> >>> Haven't used "qom-get" before, but it seems to fetch one property
> >>> for a specific object. If so, will it be strange to hide some
> >>> capability bits into every GIC objects (though there is possibly
> >>> one object)?
> >>
> >> Pardon my ignorance...  what are these "GIC objects"?
> >>
> >> What exactly is the "GIC type", and how would the result of
> >> query-gic-capability be used?
> >
> > The GIC type (for our purposes) is the revision of the interrupt
> > controller supported by the host, which comes in two versions
> > (v2 and v3). These are not compatible, unless your host has
> > the v3-with-v2-compat flavour. If a host is v3-only, it is not
> > possible for it to give the guest a v2 virtual interrupt
> > controller; if v2, it can't give the guest a v3 virtual interrupt
> > controller. (If you ask QEMU to do this via command line options
> > we will report an error at startup.)
> 
> How would the command line look like?
>

Here is what is available today

# select gicv2 (this work with and without KVM)
qemu-system-aarch64 -M virt                      # v2 is the default
qemu-system-aarch64 -M virt,gic-version=2 ...

# select gicv3 (only works with KVM)
qemu-system-aarch64 -M virt,gic-version=3 ...

# select whatever the host has
qemu-system-aarch64 -M virt,gic-version=host ...


Thanks,
drew