kvm-irqchip: introduce new API to support route change

Paolo suggested adding the new API to support route changes [1]. We should invoke
kvm_irqchip_begin_route_changes() before changing the routes, increasing the
KVMRouteChange.changes if the routes are changed, and commit the changes at last.

[1] https://lists.gnu.org/archive/html/qemu-devel/2021-11/msg02898.html

Signed-off-by: Longpeng <longpeng2@huawei.com>
Message-Id: <20220222141116.2091-2-longpeng2@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/sysemu/kvm.h

@@ -224,6 +224,11 @@ DECLARE_INSTANCE_CHECKER(KVMState, KVM_STATE,
 extern KVMState *kvm_state;
 typedef struct Notifier Notifier;
 
+typedef struct KVMRouteChange {
+     KVMState *s;
+     int changes;
+} KVMRouteChange;
+
 /* external API */
 
 bool kvm_has_free_slot(MachineState *ms);
@@ -494,6 +499,20 @@ int kvm_irqchip_add_msi_route(KVMState *s, int vector, PCIDevice *dev);
 int kvm_irqchip_update_msi_route(KVMState *s, int virq, MSIMessage msg,
                                  PCIDevice *dev);
 void kvm_irqchip_commit_routes(KVMState *s);
+
+static inline KVMRouteChange kvm_irqchip_begin_route_changes(KVMState *s)
+{
+    return (KVMRouteChange) { .s = s, .changes = 0 };
+}
+
+static inline void kvm_irqchip_commit_route_changes(KVMRouteChange *c)
+{
+    if (c->changes) {
+        kvm_irqchip_commit_routes(c->s);
+        c->changes = 0;
+    }
+}
+
 void kvm_irqchip_release_virq(KVMState *s, int virq);
 
 int kvm_irqchip_add_adapter_route(KVMState *s, AdapterInfo *adapter);