Re: [PATCH 1/5] qapi/qom: Introduce kvm-pmu-filter object

[Markus Armbruster <armbru@redhat.com>]

Zhao Liu <zhao1.liu@intel.com> writes:

> Hi Markus
>
> On Thu, Apr 10, 2025 at 04:21:01PM +0200, Markus Armbruster wrote:
>> Date: Thu, 10 Apr 2025 16:21:01 +0200
>> From: Markus Armbruster <armbru@redhat.com>
>> Subject: Re: [PATCH 1/5] qapi/qom: Introduce kvm-pmu-filter object
>> 
>> Zhao Liu <zhao1.liu@intel.com> writes:
>> 
>> > Introduce the kvm-pmu-filter object and support the PMU event with raw
>> > format.
>> 
>> Remind me, what does the kvm-pmu-filter object do, and why would we
>> want to use it?
>
> KVM PMU filter allows user space to set PMU event whitelist / blacklist
> for Guest. Both ARM and x86's KVMs accept a list of PMU events, and x86
> also accpets other formats & fixed counter field.

But what does the system *do* with these event lists?

> The earliest version uses custom parsing rules, which is not flexible
> enough to scale. So to support such complex configuration in cli, it's
> best to define and parse it via QAPI, and it's best to support the JSON
> way.
>
> Based on these considerations, I found "object" to be a suitable enough
> choice.
>
> Thus kvm-pmu-filter object handles all the complexity of parsing values
> from cli, and it can include some checks that QAPI cannot include (such
> as the 12-bit limit).
>
> Thanks,
> Zhao