Re: [PATCH v8] arm/kvm: Enable support for KVM_ARM_VCPU_PMU_V3_FILTER

[Daniel P . Berrangé]

On Tue, Apr 02, 2024 at 03:01:50PM +0200, Kevin Wolf wrote:
> Am 29.03.2024 um 04:45 hat Shaoqin Huang geschrieben:
> > Hi Daniel,
> > 
> > On 3/25/24 16:55, Daniel P. Berrangé wrote:
> > > On Mon, Mar 25, 2024 at 01:35:58PM +0800, Shaoqin Huang wrote:
> > > > Hi Daniel,
> > > > 
> > > > Thanks for your reviewing. I see your comments in the v7.
> > > > 
> > > > I have some doubts about what you said about the QAPI. Do you want me to
> > > > convert the current design into the QAPI parsing like the
> > > > IOThreadVirtQueueMapping? And we need to add new json definition in the
> > > > qapi/ directory?
> > 
> > I have defined the QAPI for kvm-pmu-filter like below:

> > @@ -2439,6 +2441,7 @@ static Property arm_cpu_properties[] = {
> >                          mp_affinity, ARM64_AFFINITY_INVALID),
> >      DEFINE_PROP_INT32("node-id", ARMCPU, node_id, CPU_UNSET_NUMA_NODE_ID),
> >      DEFINE_PROP_INT32("core-count", ARMCPU, core_count, -1),
> > +    DEFINE_PROP_KVM_PMU_FILTER("kvm-pmu-filter", ARMCPU, kvm_pmu_filter),
> >      DEFINE_PROP_END_OF_LIST()
> >  };
> > 
> > And I guess I can use the new json format input like below:
> > 
> > qemu-system-aarch64 \
> >     -cpu host, '{"filter": [{"action": "a", "start": 0x10, "end": "0x11"}]}'
> > 
> > But it doesn't work. It seems like because the -cpu option doesn't
> > support json format parameter.
> > 
> > Maybe I'm wrong. So I want to double check with if the -cpu option
> > support json format nowadays?
> 
> As far as I can see, -cpu doesn't support JSON yet. But even if it did,
> your command line would be invalid because the 'host,' part isn't JSON.
> 
> > If the -cpu option doesn't support json format, how I can use the QAPI
> > for kvm-pmu-filter property?
> 
> This would probably mean QAPIfying all CPUs first, which sounds like a
> major effort.

I wonder if we can do a half-way house where we parse the JSON and
turn it into regular QemuOpts internally, and then just use QAPI
parsing for the filter property. IOW, publically give the illusion
that -cpu has been QAPI-ified, but without actually doing the hard
part yet. The idea being to avoid inventing a new cli syntax that
has no analogue to QAPI.
With regards,
Daniel
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