From: Markus Armbruster <armbru@redhat.com>
References: <1455428503-2113-1-git-send-email-peterx@redhat.com>
Date: Mon, 15 Feb 2016 10:52:01 +0100
In-Reply-To: <1455428503-2113-1-git-send-email-peterx@redhat.com> (Peter Xu's
	message of "Sun, 14 Feb 2016 13:41:41 +0800")
Message-ID: <87povy5mim.fsf@blackfin.pond.sub.org>
MIME-Version: 1.0
Content-Type: text/plain
Subject: Re: [Qemu-devel] [RFC PATCH 0/2] ARM: add QMP command to query GIC
	version
To: Peter Xu <peterx@redhat.com>
Cc: libvir-list@redhat.com, wei@redhat.com, drjones@redhat.com, qemu-devel@nongnu.org, abologna@redhat.com

Peter Xu <peterx@redhat.com> writes:

> For ARM platform, we still do not have any interface to query
> whether current QEMU/host support specific GIC version. This
> patchset is trying to add one QMP interface for that. By querying
> the GIC capability using the new interface, one should know exactly
> what GIC version(s) the platform will support. The capability bits
> will be decided by both QEMU and host kernel.
>
> The current patchset only provides interface for review. Its handler
> is a fake one which returns empty always.
>
> The command interface I am planning to add is something like this:
>
> -> { "execute": "query-gic-capability" }
> <- { "return": [ "gicv2", "gicv2-kvm", "gicv3-kvm" ] }
>
> Currently, all the possible supported GIC versions are:
>
> - gicv2:      GIC version 2 without kernel IRQ chip
> - gicv2-kvm:  GIC version 2 with kernel IRQ chip
> - gicv3:      GIC version 3 without kernel IRQ chip (not supported)
> - gicv3-kvm:  GIC version 3 with kernel IRQ chip
>
> Since "gicv3" is still not supported (to use GICv3, kernel irqchip
> support is required for now, which corresponds to "gicv3-kvm"),
> currently the maximum superset of the result should be:
>
> ["gicv2", "gicv2-kvm", "gicv3-kvm"]
>
> Please help review whether the interface suits our need, also please
> point out any error I have made.

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?

> One question: how should I make this command "ARM only"? I see that
> in qmp-commands.hx, I can use something like "#if defined
> TARGET_ARM" to block out ARM specified commands, however how should
> I do the similiar thing in qapi-schema.json?

Have a look at the #if in qmp-commands.hx.