[v3,4/5] hostmem: hostmem listener pin RAM-Device by refcnt

diff --git a/hw/virtio/dataplane/hostmem.c b/hw/virtio/dataplane/hostmem.c
index f31a703..420c9be 100644
--- a/hw/virtio/dataplane/hostmem.c
+++ b/hw/virtio/dataplane/hostmem.c
@@ -42,18 +42,23 @@  static void hostmem_ref(HostMem *hostmem)
 
 static void hostmem_unref(HostMem *hostmem)
 {
-    int t;
+    int i, t;
+    HostMemRegion *hmr;
 
     t = __sync_sub_and_fetch(&hostmem->ref, 1);
     assert(t >= 0);
     if (!t) {
+        for (i = 0; i < hostmem->num_current_regions; i++) {
+            hmr = &hostmem->current_regions[i];
+            memory_region_unref(hmr->mr);
+        }
         g_free(hostmem->current_regions);
         g_free(hostmem);
     }
 }
 
 static void *address_space_mem_lookup(AddrSpaceMem *as_mem, hwaddr phys,
-    hwaddr len, bool is_write)
+    hwaddr len, MemoryRegion **mr, bool is_write)
 {
     HostMemRegion *region;
     void *host_addr = NULL;
@@ -65,6 +70,9 @@  static void *address_space_mem_lookup(AddrSpaceMem *as_mem, hwaddr phys,
     hostmem_ref(hostmem);
     qemu_mutex_unlock(&as_mem->cur_lock);
 
+    if (mr) {
+        *mr = NULL;
+    }
     region = bsearch(&phys, hostmem->current_regions,
                      hostmem->num_current_regions,
                      sizeof(hostmem->current_regions[0]),
@@ -79,7 +87,10 @@  static void *address_space_mem_lookup(AddrSpaceMem *as_mem, hwaddr phys,
     if (len <= region->size - offset_within_region) {
         host_addr = region->host_addr + offset_within_region;
     }
-
+    if (mr) {
+        *mr = region->mr;
+        memory_region_ref(*mr);
+    }
 out:
     hostmem_unref(hostmem);
     return host_addr;
@@ -88,9 +99,10 @@  out:
 /**
  * Map guest physical address to host pointer
  */
-void *hostmem_lookup(hwaddr phys, hwaddr len, bool is_write)
+void *hostmem_lookup(hwaddr phys, hwaddr len, MemoryRegion **mr,
+    bool is_write)
 {
-    return address_space_mem_lookup(system_mem, phys, len, is_write);
+    return address_space_mem_lookup(system_mem, phys, len, mr, is_write);
 }
 
 static void hostmem_listener_begin(MemoryListener *listener)
@@ -134,6 +146,7 @@  static void hostmem_append_new_region(HostMem *hostmem,
     hostmem->current_regions[num] = (HostMemRegion){
         .host_addr = ram_ptr + section->offset_within_region,
         .guest_addr = section->offset_within_address_space,
+        .mr = section->mr,
         .size = section->size,
         .readonly = section->readonly,
     };
@@ -155,6 +168,7 @@  static void hostmem_listener_append_region(MemoryListener *listener,
         return;
     }
 
+    memory_region_ref(section->mr);
     hostmem_append_new_region(as_mem->next_hostmem, section);
 }
 
diff --git a/hw/virtio/dataplane/vring.c b/hw/virtio/dataplane/vring.c
index 4d6d735..e3c3afb 100644
--- a/hw/virtio/dataplane/vring.c
+++ b/hw/virtio/dataplane/vring.c
@@ -27,7 +27,7 @@  bool vring_setup(Vring *vring, VirtIODevice *vdev, int n)
 
     vring->broken = false;
 
-    vring_ptr = hostmem_lookup(vring_addr, vring_size, true);
+    vring_ptr = hostmem_lookup(vring_addr, vring_size, NULL, true);
     if (!vring_ptr) {
         error_report("Failed to map vring "
                      "addr %#" HWADDR_PRIx " size %" HWADDR_PRIu,
@@ -137,7 +137,7 @@  static int get_indirect(Vring *vring,
 
         /* Translate indirect descriptor */
         desc_ptr = hostmem_lookup(indirect->addr + found * sizeof(desc),
-                                  sizeof(desc), false);
+                                  sizeof(desc), NULL, false);
         if (!desc_ptr) {
             error_report("Failed to map indirect descriptor "
                          "addr %#" PRIx64 " len %zu",
@@ -169,7 +169,7 @@  static int get_indirect(Vring *vring,
             return -ENOBUFS;
         }
 
-        iov->iov_base = hostmem_lookup(desc.addr, desc.len,
+        iov->iov_base = hostmem_lookup(desc.addr, desc.len, NULL,
                                        desc.flags & VRING_DESC_F_WRITE);
         if (!iov->iov_base) {
             error_report("Failed to map indirect descriptor"
@@ -297,7 +297,7 @@  int vring_pop(VirtIODevice *vdev, Vring *vring,
         }
 
         /* TODO handle non-contiguous memory across region boundaries */
-        iov->iov_base = hostmem_lookup(desc.addr, desc.len,
+        iov->iov_base = hostmem_lookup(desc.addr, desc.len, NULL,
                                        desc.flags & VRING_DESC_F_WRITE);
         if (!iov->iov_base) {
             error_report("Failed to map vring desc addr %#" PRIx64 " len %u",
diff --git a/include/hw/virtio/dataplane/hostmem.h b/include/hw/virtio/dataplane/hostmem.h
index d04ce55..094102b 100644
--- a/include/hw/virtio/dataplane/hostmem.h
+++ b/include/hw/virtio/dataplane/hostmem.h
@@ -21,6 +21,7 @@ 
 typedef struct {
     void *host_addr;
     hwaddr guest_addr;
+    MemoryRegion *mr;
     uint64_t size;
     bool readonly;
 } HostMemRegion;
@@ -52,7 +53,8 @@  typedef struct {
  * can be done with other mechanisms like bdrv_drain_all() that quiesce
  * in-flight I/O.
  */
-void *hostmem_lookup(hwaddr phys, hwaddr len, bool is_write);
+void *hostmem_lookup(hwaddr phys, hwaddr len, MemoryRegion **mr,
+    bool is_write);
 void hostmem_init(void);
 
 #else