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

[Philippe Mathieu-Daudé]

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....@intel.com>
Tested-by: Yi Lai <yi1....@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;
  };