memory: Split zones when do coalesced_io_del()

It is a workaround of current KVM's KVM_UNREGISTER_COALESCED_MMIO
interface.  The kernel interface only allows to unregister an mmio
device with exactly the zone size when registered, or any smaller zone
that is included in the device mmio zone.  It does not support the
userspace to specify a very large zone to remove all the small mmio
devices within the zone covered.

Logically speaking it would be nicer to fix this from KVM side, though
in all cases we still need to coop with old kernels so let's do this.

Fixes: 3ac7d43
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20190820141328.10009-2-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

memory.c

@@ -855,8 +855,39 @@ static void address_space_update_ioeventfds(AddressSpace *as)
     flatview_unref(view);
 }
 
+/*
+ * Notify the memory listeners about the coalesced IO change events of
+ * range `cmr'.  Only the part that has intersection of the specified
+ * FlatRange will be sent.
+ */
+static void flat_range_coalesced_io_notify(FlatRange *fr, AddressSpace *as,
+                                           CoalescedMemoryRange *cmr, bool add)
+{
+    AddrRange tmp;
+
+    tmp = addrrange_shift(cmr->addr,
+                          int128_sub(fr->addr.start,
+                                     int128_make64(fr->offset_in_region)));
+    if (!addrrange_intersects(tmp, fr->addr)) {
+        return;
+    }
+    tmp = addrrange_intersection(tmp, fr->addr);
+
+    if (add) {
+        MEMORY_LISTENER_UPDATE_REGION(fr, as, Forward, coalesced_io_add,
+                                      int128_get64(tmp.start),
+                                      int128_get64(tmp.size));
+    } else {
+        MEMORY_LISTENER_UPDATE_REGION(fr, as, Reverse, coalesced_io_del,
+                                      int128_get64(tmp.start),
+                                      int128_get64(tmp.size));
+    }
+}
+
 static void flat_range_coalesced_io_del(FlatRange *fr, AddressSpace *as)
 {
+    CoalescedMemoryRange *cmr;
+
     if (!fr->has_coalesced_range) {
         return;
     }
@@ -865,16 +896,15 @@ static void flat_range_coalesced_io_del(FlatRange *fr, AddressSpace *as)
         return;
     }
 
-    MEMORY_LISTENER_UPDATE_REGION(fr, as, Reverse, coalesced_io_del,
-                                  int128_get64(fr->addr.start),
-                                  int128_get64(fr->addr.size));
+    QTAILQ_FOREACH(cmr, &fr->mr->coalesced, link) {
+        flat_range_coalesced_io_notify(fr, as, cmr, false);
+    }
 }
 
 static void flat_range_coalesced_io_add(FlatRange *fr, AddressSpace *as)
 {
     MemoryRegion *mr = fr->mr;
     CoalescedMemoryRange *cmr;
-    AddrRange tmp;
 
     if (QTAILQ_EMPTY(&mr->coalesced)) {
         return;
@@ -885,16 +915,7 @@ static void flat_range_coalesced_io_add(FlatRange *fr, AddressSpace *as)
     }
 
     QTAILQ_FOREACH(cmr, &mr->coalesced, link) {
-        tmp = addrrange_shift(cmr->addr,
-                              int128_sub(fr->addr.start,
-                                         int128_make64(fr->offset_in_region)));
-        if (!addrrange_intersects(tmp, fr->addr)) {
-            continue;
-        }
-        tmp = addrrange_intersection(tmp, fr->addr);
-        MEMORY_LISTENER_UPDATE_REGION(fr, as, Forward, coalesced_io_add,
-                                      int128_get64(tmp.start),
-                                      int128_get64(tmp.size));
+        flat_range_coalesced_io_notify(fr, as, cmr, true);
     }
 }