Re: [PATCH 5/5] i386/kvm: Support fixed counter in KVM PMU filter

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 9/4/25 10:26, Zhao Liu wrote:
> KVM_SET_PMU_EVENT_FILTER of x86 KVM allows user to configure x86 fixed
> function counters by a bitmap.
> 
> Add the support of x86-fixed-counter in kvm-pmu-filter object and handle
> this in i386 kvm codes.
> 
> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
> Tested-by: Yi Lai <yi1.lai@intel.com>
> ---
> Changes since RFC v2:
>   * Drop KVMPMUX86FixedCounter structure and use uint32_t to represent
>     bitmap in QAPI directly.
>   * Add Tested-by from Yi.
>   * Add documentation in qemu-options.hx.
>   * Bump up the supported QAPI version to v10.1.
> 
> Changes since RFC v1:
>   * Make "action" as a global (per filter object) item, not a per-counter
>     parameter. (Dapeng)
>   * Bump up the supported QAPI version to v10.0.
> ---
>   accel/kvm/kvm-pmu.c      | 31 +++++++++++++++++++++++++++++++
>   include/system/kvm-pmu.h |  5 ++++-
>   qapi/kvm.json            |  6 +++++-
>   qemu-options.hx          |  6 +++++-
>   target/i386/kvm/kvm.c    | 39 ++++++++++++++++++++++++---------------
>   5 files changed, 69 insertions(+), 18 deletions(-)
> 
> diff --git a/accel/kvm/kvm-pmu.c b/accel/kvm/kvm-pmu.c
> index 9205907d1779..509d69d9c515 100644
> --- a/accel/kvm/kvm-pmu.c
> +++ b/accel/kvm/kvm-pmu.c
> @@ -101,6 +101,29 @@ fail:
>       qapi_free_KvmPmuFilterEventList(head);
>   }
>   
> +static void kvm_pmu_filter_get_fixed_counter(Object *obj, Visitor *v,
> +                                             const char *name, void *opaque,
> +                                             Error **errp)
> +{
> +    KVMPMUFilter *filter = KVM_PMU_FILTER(obj);
> +
> +    visit_type_uint32(v, name, &filter->x86_fixed_counter, errp);
> +}
> +
> +static void kvm_pmu_filter_set_fixed_counter(Object *obj, Visitor *v,
> +                                             const char *name, void *opaque,
> +                                             Error **errp)
> +{
> +    KVMPMUFilter *filter = KVM_PMU_FILTER(obj);
> +    uint32_t counter;
> +
> +    if (!visit_type_uint32(v, name, &counter, errp)) {
> +        return;
> +    }
> +
> +    filter->x86_fixed_counter = counter;
> +}
> +
>   static void kvm_pmu_filter_class_init(ObjectClass *oc, void *data)
>   {
>       object_class_property_add_enum(oc, "action", "KvmPmuFilterAction",
> @@ -116,6 +139,14 @@ static void kvm_pmu_filter_class_init(ObjectClass *oc, void *data)
>                                 NULL, NULL);
>       object_class_property_set_description(oc, "events",
>                                             "KVM PMU event list");
> +
> +    object_class_property_add(oc, "x86-fixed-counter", "uint32_t",
> +                              kvm_pmu_filter_get_fixed_counter,
> +                              kvm_pmu_filter_set_fixed_counter,
> +                              NULL, NULL);
> +    object_class_property_set_description(oc, "x86-fixed-counter",
> +                                          "Enablement bitmap of "
> +                                          "x86 PMU fixed counter");

Adding that x86-specific field to all architectures is a bit dubious.

>   }
>   
>   static void kvm_pmu_filter_instance_init(Object *obj)
> diff --git a/include/system/kvm-pmu.h b/include/system/kvm-pmu.h
> index 6abc0d037aee..5238b2b4dcc7 100644
> --- a/include/system/kvm-pmu.h
> +++ b/include/system/kvm-pmu.h
> @@ -19,10 +19,12 @@ OBJECT_DECLARE_SIMPLE_TYPE(KVMPMUFilter, KVM_PMU_FILTER)
>   
>   /**
>    * KVMPMUFilter:
> - * @action: action that KVM PMU filter will take for selected PMU events.
> + * @action: action that KVM PMU filter will take for selected PMU events
> + *    and counters.
>    * @nevents: number of PMU event entries listed in @events
>    * @events: list of PMU event entries.  A PMU event entry may represent one
>    *    event or multiple events due to its format.
> + * @x86_fixed_counter: bitmap of x86 fixed counter.
>    */
>   struct KVMPMUFilter {
>       Object parent_obj;
> @@ -30,6 +32,7 @@ struct KVMPMUFilter {
>       KvmPmuFilterAction action;
>       uint32_t nevents;
>       KvmPmuFilterEventList *events;
> +    uint32_t x86_fixed_counter;
>   };