[Qemu-devel] [PATCH 24/40] memory: add getter/setter for owner

[Paolo Bonzini]

Whenever memory regions are accessed outside the BQL, they need to be
preserved against hot-unplug.  MemoryRegions actually do not have their
own reference count; they piggyback on a QOM object, their "owner".
Add two functions to retrieve and specify the owner.

The setter function will affect the owner recursively on a whole tree
of contained regions, but without crossing (a) aliases (b) regions that
are already owned by another device.  This is so that a device can create
a complex tree of regions and a single call to memory_region_set_owner
(perhaps even within a bus-specific function, e.g. pci_register_bar) will
affect the entire tree.

Signed-off-by: Paolo Bonzini <address@hidden>
---
 include/exec/memory.h |   18 ++++++++++++++++++
 memory.c              |   21 +++++++++++++++++++++
 2 files changed, 39 insertions(+), 0 deletions(-)

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 06586f3..5c20bac 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -135,6 +135,7 @@ struct MemoryRegion {
     const MemoryRegionIOMMUOps *iommu_ops;
     void *opaque;
     MemoryRegion *parent;
+    struct Object *owner;
     Int128 size;
     hwaddr addr;
     void (*destructor)(MemoryRegion *mr);
@@ -374,6 +375,23 @@ void memory_region_init_iommu(MemoryRegion *mr,
 void memory_region_destroy(MemoryRegion *mr);
 
 /**
+ * memory_region_owner: get a memory region's owner.
+ *
+ * @mr: the memory region being queried.
+ */
+struct Object *memory_region_owner(MemoryRegion *mr);
+
+/**
+ * memory_region_set_owner: set the owner for a memory region and all
+ * the unowned regions below it.
+ *
+ * @mr: the memory region being set.
+ * @owner: the object that acts as the owner
+ */
+void memory_region_set_owner(MemoryRegion *mr,
+                             struct Object *owner);
+
+/**
  * memory_region_size: get a memory region's size.
  *
  * @mr: the memory region being queried.
diff --git a/memory.c b/memory.c
index 00e31c0..f7fddb1 100644
--- a/memory.c
+++ b/memory.c
@@ -789,6 +789,7 @@ void memory_region_init(MemoryRegion *mr,
     mr->ops = NULL;
     mr->iommu_ops = NULL;
     mr->parent = NULL;
+    mr->owner = NULL;
     mr->size = int128_make64(size);
     if (size == UINT64_MAX) {
         mr->size = int128_2_64();
@@ -1040,6 +1041,26 @@ void memory_region_destroy(MemoryRegion *mr)
     g_free(mr->ioeventfds);
 }
 
+Object *memory_region_owner(MemoryRegion *mr)
+{
+    return mr->owner;
+}
+
+void memory_region_set_owner(MemoryRegion *mr,
+                             Object *owner)
+{
+    MemoryRegion *child;
+
+    assert(mr->owner == NULL || mr->owner == owner);
+    mr->owner = owner;
+
+    QTAILQ_FOREACH(child, &mr->subregions, subregions_link) {
+        if (child->owner == NULL || child->owner == owner) {
+            memory_region_set_owner(child, owner);
+        }
+    }
+}
+
 uint64_t memory_region_size(MemoryRegion *mr)
 {
     if (int128_eq(mr->size, int128_2_64())) {
-- 
1.7.1