On Mon, Feb 15, 2016 at 10:52:01AM +0100, Markus Armbruster wrote:
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?
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)? I agree that we should keep the interface as simple as possible. I see that there are already commands that works just like this one, which is to query some capabilities from QEMU, like: - query-dump-guest-memory-capability - query-migrate-capabilities So... besides the original proposal, what about adding a generic QMP command to query all kinds of capabilities (and let GIC be the first item)? Or any other way to avoid adding a new command? Thanks. Peter
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.