[Qemu-devel] [PATCH v2 04/17] exec: add a reference to the region returned by address_space_translate

[Paolo Bonzini <pbonzini@redhat.com>]

Once address_space_translate will only be protected by RCU, the returned
MemoryRegion can disappear as soon as the RCU read-side critical
section ends.  Avoid this by adding a reference to the region, and
dropping it in the caller of address_space_translate.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 exec.c                | 16 ++++++++++++++--
 include/exec/memory.h |  3 ++-
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/exec.c b/exec.c
index ba50e8d..bf287cb 100644
--- a/exec.c
+++ b/exec.c
@@ -292,6 +292,7 @@ MemoryRegion *address_space_translate(AddressSpace *as, hwaddr addr,
 
     *plen = len;
     *xlat = addr;
+    memory_region_ref(mr);
     return mr;
 }
 
@@ -1994,6 +1995,7 @@ bool address_space_rw(AddressSpace *as, hwaddr addr, uint8_t *buf,
                 memcpy(buf, ptr, l);
             }
         }
+        memory_region_unref(mr);
         len -= l;
         buf += l;
         addr += l;
@@ -2159,8 +2161,10 @@ void *address_space_map(AddressSpace *as,
             raddr = memory_region_get_ram_addr(mr) + xlat;
         } else {
             if (memory_region_get_ram_addr(mr) + xlat != raddr + todo) {
+                memory_region_unref(mr);
                 break;
             }
+            memory_region_unref(mr);
         }
 
         len -= l;
@@ -2260,6 +2264,7 @@ static inline uint32_t ldl_phys_internal(hwaddr addr,
             break;
         }
     }
+    memory_region_unref(mr);
     return val;
 }
 
@@ -2319,6 +2324,7 @@ static inline uint64_t ldq_phys_internal(hwaddr addr,
             break;
         }
     }
+    memory_region_unref(mr);
     return val;
 }
 
@@ -2386,6 +2392,7 @@ static inline uint32_t lduw_phys_internal(hwaddr addr,
             break;
         }
     }
+    memory_region_unref(mr);
     return val;
 }
 
@@ -2433,6 +2440,7 @@ void stl_phys_notdirty(hwaddr addr, uint32_t val)
             }
         }
     }
+    memory_region_unref(mr);
 }
 
 /* warning: addr must be aligned */
@@ -2474,6 +2482,7 @@ static inline void stl_phys_internal(hwaddr addr, uint32_t val,
         }
         invalidate_and_set_dirty(addr1, 4);
     }
+    memory_region_unref(mr);
 }
 
 void stl_phys(hwaddr addr, uint32_t val)
@@ -2537,6 +2546,7 @@ static inline void stw_phys_internal(hwaddr addr, uint32_t val,
         }
         invalidate_and_set_dirty(addr1, 2);
     }
+    memory_region_unref(mr);
 }
 
 void stw_phys(hwaddr addr, uint32_t val)
@@ -2626,11 +2636,13 @@ bool cpu_physical_memory_is_io(hwaddr phys_addr)
 {
     MemoryRegion*mr;
     hwaddr l = 1;
+    bool res;
 
     mr = address_space_translate(&address_space_memory,
                                  phys_addr, &phys_addr, &l, false);
 
-    return !(memory_region_is_ram(mr) ||
-             memory_region_is_romd(mr));
+    res = !(memory_region_is_ram(mr) || memory_region_is_romd(mr));
+    memory_region_unref(mr);
+    return res;
 }
 #endif
diff --git a/include/exec/memory.h b/include/exec/memory.h
index bfcdf65..a2546b7 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -1015,7 +1015,8 @@ bool address_space_write(AddressSpace *as, hwaddr addr,
 bool address_space_read(AddressSpace *as, hwaddr addr, uint8_t *buf, int len);
 
 /* address_space_translate: translate an address range into an address space
- * into a MemoryRegion and an address range into that section
+ * into a MemoryRegion and an address range into that section.  Add a reference
+ * to that region.
  *
  * @as: #AddressSpace to be accessed
  * @addr: address within that address space
-- 
1.8.1.4