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

[Wei Huang <wei@redhat.com>]

On 2/13/16 23:41, Peter Xu wrote:
> 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.

I tested QEMU with these patches and they were able to work on a native
ARM64 machine.

> 
> 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?

This situation is similar to "rtc-reset-reinjection", right? I think You
can disable this feature on other arch's by setting
QERR_FEATURE_DISABLED in file like monitor.c.

> 
> Thanks!
> Peter
> 
> Peter Xu (2):
>   arm: gic: add GICType
>   arm: gic: add "query-gic-capability" interface
> 
>  qapi-schema.json | 28 ++++++++++++++++++++++++++++
>  qmp-commands.hx  | 25 +++++++++++++++++++++++++
>  qmp.c            |  5 +++++
>  scripts/qapi.py  |  1 +
>  4 files changed, 59 insertions(+)
>