memory: allow memory_region_find() to run on non-root memory regions

memory_region_find() is similar to registering a MemoryListener and
checking for the MemoryRegionSections that come from a particular
region.  There is no reason for this to be limited to a root memory
region.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

2 files changed, 34 insertions, 14 deletions

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 9e88320113..329ffb191d 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -718,24 +718,34 @@ void memory_region_set_alias_offset(MemoryRegion *mr,
                                     hwaddr offset);
 
 /**
- * memory_region_find: locate a MemoryRegion in an address space
+ * memory_region_find: translate an address/size relative to a
+ * MemoryRegion into a #MemoryRegionSection.
  *
- * Locates the first #MemoryRegion within an address space given by
- * @address_space that overlaps the range given by @addr and @size.
+ * Locates the first #MemoryRegion within @mr that overlaps the range
+ * given by @addr and @size.
  *
  * Returns a #MemoryRegionSection that describes a contiguous overlap.
  * It will have the following characteristics:
- *    .@offset_within_address_space >= @addr
- *    .@offset_within_address_space + .@size <= @addr + @size
  *    .@size = 0 iff no overlap was found
  *    .@mr is non-%NULL iff an overlap was found
  *
- * @address_space: a top-level (i.e. parentless) region that contains
- *       the region to be found
- * @addr: start of the area within @address_space to be searched
+ * Remember that in the return value the @offset_within_region is
+ * relative to the returned region (in the .@mr field), not to the
+ * @mr argument.
+ *
+ * Similarly, the .@offset_within_address_space is relative to the
+ * address space that contains both regions, the passed and the
+ * returned one.  However, in the special case where the @mr argument
+ * has no parent (and thus is the root of the address space), the
+ * following will hold:
+ *    .@offset_within_address_space >= @addr
+ *    .@offset_within_address_space + .@size <= @addr + @size
+ *
+ * @mr: a MemoryRegion within which @addr is a relative address
+ * @addr: start of the area within @as to be searched
  * @size: size of the area to be searched
  */
-MemoryRegionSection memory_region_find(MemoryRegion *address_space,
+MemoryRegionSection memory_region_find(MemoryRegion *mr,
                                        hwaddr addr, uint64_t size);
 
 /**
diff --git a/memory.c b/memory.c
index 75ca281e97..34bfb13894 100644
--- a/memory.c
+++ b/memory.c
@@ -1451,15 +1451,24 @@ static FlatRange *address_space_lookup(AddressSpace *as, AddrRange addr)
                    sizeof(FlatRange), cmp_flatrange_addr);
 }
 
-MemoryRegionSection memory_region_find(MemoryRegion *address_space,
+MemoryRegionSection memory_region_find(MemoryRegion *mr,
                                        hwaddr addr, uint64_t size)
 {
-    AddressSpace *as = memory_region_to_address_space(address_space);
-    AddrRange range = addrrange_make(int128_make64(addr),
-                                     int128_make64(size));
-    FlatRange *fr = address_space_lookup(as, range);
     MemoryRegionSection ret = { .mr = NULL, .size = 0 };
+    MemoryRegion *root;
+    AddressSpace *as;
+    AddrRange range;
+    FlatRange *fr;
+
+    addr += mr->addr;
+    for (root = mr; root->parent; ) {
+        root = root->parent;
+        addr += root->addr;
+    }
 
+    as = memory_region_to_address_space(root);
+    range = addrrange_make(int128_make64(addr), int128_make64(size));
+    fr = address_space_lookup(as, range);
     if (!fr) {
         return ret;
     }
@@ -1470,6 +1479,7 @@ MemoryRegionSection memory_region_find(MemoryRegion *address_space,
     }
 
     ret.mr = fr->mr;
+    ret.address_space = as;
     range = addrrange_intersection(range, fr->addr);
     ret.offset_within_region = fr->offset_in_region;
     ret.offset_within_region += int128_get64(int128_sub(range.start,