[v6,2/3] memory: introduce IOMMUOps.notify_flag_changed

diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index 28c31a2..9d49be7 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -1974,7 +1974,9 @@  static IOMMUTLBEntry vtd_iommu_translate(MemoryRegion *iommu, hwaddr addr,
     return ret;
 }
 
-static void vtd_iommu_notify_started(MemoryRegion *iommu)
+static void vtd_iommu_notify_flag_changed(MemoryRegion *iommu,
+                                          IOMMUNotifierFlag old,
+                                          IOMMUNotifierFlag new)
 {
     VTDAddressSpace *vtd_as = container_of(iommu, VTDAddressSpace, iommu);
 
@@ -2348,7 +2350,7 @@  static void vtd_init(IntelIOMMUState *s)
     memset(s->womask, 0, DMAR_REG_SIZE);
 
     s->iommu_ops.translate = vtd_iommu_translate;
-    s->iommu_ops.notify_started = vtd_iommu_notify_started;
+    s->iommu_ops.notify_flag_changed = vtd_iommu_notify_flag_changed;
     s->root = 0;
     s->root_extended = false;
     s->dmar_enabled = false;
diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
index f20b0b8..ae30bbe 100644
--- a/hw/ppc/spapr_iommu.c
+++ b/hw/ppc/spapr_iommu.c
@@ -156,14 +156,17 @@  static uint64_t spapr_tce_get_min_page_size(MemoryRegion *iommu)
     return 1ULL << tcet->page_shift;
 }
 
-static void spapr_tce_notify_started(MemoryRegion *iommu)
+static void spapr_tce_notify_flag_changed(MemoryRegion *iommu,
+                                          IOMMUNotifierFlag old,
+                                          IOMMUNotifierFlag new)
 {
-    spapr_tce_set_need_vfio(container_of(iommu, sPAPRTCETable, iommu), true);
-}
+    struct sPAPRTCETable *tbl = container_of(iommu, sPAPRTCETable, iommu);
 
-static void spapr_tce_notify_stopped(MemoryRegion *iommu)
-{
-    spapr_tce_set_need_vfio(container_of(iommu, sPAPRTCETable, iommu), false);
+    if (old == IOMMU_NOTIFIER_NONE && new != IOMMU_NOTIFIER_NONE) {
+        spapr_tce_set_need_vfio(tbl, true);
+    } else if (old != IOMMU_NOTIFIER_NONE && new == IOMMU_NOTIFIER_NONE) {
+        spapr_tce_set_need_vfio(tbl, false);
+    }
 }
 
 static int spapr_tce_table_post_load(void *opaque, int version_id)
@@ -246,8 +249,7 @@  static const VMStateDescription vmstate_spapr_tce_table = {
 static MemoryRegionIOMMUOps spapr_iommu_ops = {
     .translate = spapr_tce_translate_iommu,
     .get_min_page_size = spapr_tce_get_min_page_size,
-    .notify_started = spapr_tce_notify_started,
-    .notify_stopped = spapr_tce_notify_stopped,
+    .notify_flag_changed = spapr_tce_notify_flag_changed,
 };
 
 static int spapr_tce_table_realize(DeviceState *dev)
diff --git a/include/exec/memory.h b/include/exec/memory.h
index a3ec7aa..6b587e7 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -174,10 +174,10 @@  struct MemoryRegionIOMMUOps {
     IOMMUTLBEntry (*translate)(MemoryRegion *iommu, hwaddr addr, bool is_write);
     /* Returns minimum supported page size */
     uint64_t (*get_min_page_size)(MemoryRegion *iommu);
-    /* Called when the first notifier is set */
-    void (*notify_started)(MemoryRegion *iommu);
-    /* Called when the last notifier is removed */
-    void (*notify_stopped)(MemoryRegion *iommu);
+    /* Called when IOMMU Notifier flag changed */
+    void (*notify_flag_changed)(MemoryRegion *iommu,
+                                IOMMUNotifierFlag old_flags,
+                                IOMMUNotifierFlag new_flags);
 };
 
 typedef struct CoalescedMemoryRange CoalescedMemoryRange;
@@ -223,6 +223,7 @@  struct MemoryRegion {
     unsigned ioeventfd_nb;
     MemoryRegionIoeventfd *ioeventfds;
     QLIST_HEAD(, IOMMUNotifier) iommu_notify;
+    IOMMUNotifierFlag iommu_notify_flags;
 };
 
 /**
diff --git a/memory.c b/memory.c
index 69d9d9a..27a3f2f 100644
--- a/memory.c
+++ b/memory.c
@@ -1414,6 +1414,7 @@  void memory_region_init_iommu(MemoryRegion *mr,
     mr->iommu_ops = ops,
     mr->terminates = true;  /* then re-forwards */
     QLIST_INIT(&mr->iommu_notify);
+    mr->iommu_notify_flags = IOMMU_NOTIFIER_NONE;
 }
 
 static void memory_region_finalize(Object *obj)
@@ -1508,16 +1509,31 @@  bool memory_region_is_logging(MemoryRegion *mr, uint8_t client)
     return memory_region_get_dirty_log_mask(mr) & (1 << client);
 }
 
+static void memory_region_update_iommu_notify_flags(MemoryRegion *mr)
+{
+    IOMMUNotifierFlag flags = IOMMU_NOTIFIER_NONE;
+    IOMMUNotifier *iommu_notifier;
+
+    QLIST_FOREACH(iommu_notifier, &mr->iommu_notify, node) {
+        flags |= iommu_notifier->notifier_flags;
+    }
+
+    if (flags != mr->iommu_notify_flags &&
+        mr->iommu_ops->notify_flag_changed) {
+        mr->iommu_ops->notify_flag_changed(mr, mr->iommu_notify_flags,
+                                           flags);
+    }
+
+    mr->iommu_notify_flags = flags;
+}
+
 void memory_region_register_iommu_notifier(MemoryRegion *mr,
                                            IOMMUNotifier *n)
 {
     /* We need to register for at least one bitfield */
     assert(n->notifier_flags != IOMMU_NOTIFIER_NONE);
-    if (mr->iommu_ops->notify_started &&
-        QLIST_EMPTY(&mr->iommu_notify)) {
-        mr->iommu_ops->notify_started(mr);
-    }
     QLIST_INSERT_HEAD(&mr->iommu_notify, n, node);
+    memory_region_update_iommu_notify_flags(mr);
 }
 
 uint64_t memory_region_iommu_get_min_page_size(MemoryRegion *mr)
@@ -1555,10 +1571,7 @@  void memory_region_unregister_iommu_notifier(MemoryRegion *mr,
                                              IOMMUNotifier *n)
 {
     QLIST_REMOVE(n, node);
-    if (mr->iommu_ops->notify_stopped &&
-        QLIST_EMPTY(&mr->iommu_notify)) {
-        mr->iommu_ops->notify_stopped(mr);
-    }
+    memory_region_update_iommu_notify_flags(mr);
 }
 
 void memory_region_notify_iommu(MemoryRegion *mr,