diff options
| -rw-r--r-- | Documentation/virt/kvm/api.rst | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index fda7f7b0115e..67347d827242 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -5124,6 +5124,24 @@ Valid values for 'action':: #define KVM_PMU_EVENT_ALLOW 0 #define KVM_PMU_EVENT_DENY 1 +Via this API, KVM userspace can also control the behavior of the VM's fixed +counters (if any) by configuring the "action" and "fixed_counter_bitmap" fields. + +Specifically, KVM follows the following pseudo-code when determining whether to +allow the guest FixCtr[i] to count its pre-defined fixed event:: + + FixCtr[i]_is_allowed = (action == ALLOW) && (bitmap & BIT(i)) || + (action == DENY) && !(bitmap & BIT(i)); + FixCtr[i]_is_denied = !FixCtr[i]_is_allowed; + +KVM always consumes fixed_counter_bitmap, it's userspace's responsibility to +ensure fixed_counter_bitmap is set correctly, e.g. if userspace wants to define +a filter that only affects general purpose counters. + +Note, the "events" field also applies to fixed counters' hardcoded event_select +and unit_mask values. "fixed_counter_bitmap" has higher priority than "events" +if there is a contradiction between the two. + 4.121 KVM_PPC_SVM_OFF --------------------- |