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

[Zhao Liu <zhao1.liu@intel.com>]

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.

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