memory: abstract cracking of write access ops into a function

The memory API automatically cracks large reads and writes into smaller
ones when needed.  Factor out this mechanism, which is now duplicated between
memory reads and memory writes, into a function.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

memory.c

@@ -226,6 +226,65 @@ static void flatview_simplify(FlatView *view)
     }
 }
 
+static void memory_region_read_accessor(void *opaque,
+                                        target_phys_addr_t addr,
+                                        uint64_t *value,
+                                        unsigned size,
+                                        unsigned shift,
+                                        uint64_t mask)
+{
+    MemoryRegion *mr = opaque;
+    uint64_t tmp;
+
+    tmp = mr->ops->read(mr->opaque, addr, size);
+    *value |= (tmp & mask) << shift;
+}
+
+static void memory_region_write_accessor(void *opaque,
+                                         target_phys_addr_t addr,
+                                         uint64_t *value,
+                                         unsigned size,
+                                         unsigned shift,
+                                         uint64_t mask)
+{
+    MemoryRegion *mr = opaque;
+    uint64_t tmp;
+
+    tmp = (*value >> shift) & mask;
+    mr->ops->write(mr->opaque, addr, tmp, size);
+}
+
+static void access_with_adjusted_size(target_phys_addr_t addr,
+                                      uint64_t *value,
+                                      unsigned size,
+                                      unsigned access_size_min,
+                                      unsigned access_size_max,
+                                      void (*access)(void *opaque,
+                                                     target_phys_addr_t addr,
+                                                     uint64_t *value,
+                                                     unsigned size,
+                                                     unsigned shift,
+                                                     uint64_t mask),
+                                      void *opaque)
+{
+    uint64_t access_mask;
+    unsigned access_size;
+    unsigned i;
+
+    if (!access_size_min) {
+        access_size_min = 1;
+    }
+    if (!access_size_max) {
+        access_size_max = 4;
+    }
+    access_size = MAX(MIN(size, access_size_max), access_size_min);
+    access_mask = -1ULL >> (64 - access_size * 8);
+    for (i = 0; i < size; i += access_size) {
+        /* FIXME: big-endian support */
+        access(opaque, addr + i, value, access_size, i * 8, access_mask);
+    }
+}
+
 static void memory_region_prepare_ram_addr(MemoryRegion *mr);
 
 static void as_memory_range_add(AddressSpace *as, FlatRange *fr)
@@ -744,10 +803,7 @@ static uint32_t memory_region_read_thunk_n(void *_mr,
                                            unsigned size)
 {
     MemoryRegion *mr = _mr;
-    unsigned access_size, access_size_min, access_size_max;
-    uint64_t access_mask;
-    uint32_t data = 0, tmp;
-    unsigned i;
+    uint64_t data = 0;
 
     if (!memory_region_access_valid(mr, addr, size)) {
         return -1U; /* FIXME: better signalling */
@@ -758,23 +814,10 @@ static uint32_t memory_region_read_thunk_n(void *_mr,
     }
 
     /* FIXME: support unaligned access */
-
-    access_size_min = mr->ops->impl.min_access_size;
-    if (!access_size_min) {
-        access_size_min = 1;
-    }
-    access_size_max = mr->ops->impl.max_access_size;
-    if (!access_size_max) {
-        access_size_max = 4;
-    }
-    access_size = MAX(MIN(size, access_size_max), access_size_min);
-    access_mask = -1ULL >> (64 - access_size * 8);
-    addr += mr->offset;
-    for (i = 0; i < size; i += access_size) {
-        /* FIXME: big-endian support */
-        tmp = mr->ops->read(mr->opaque, addr + i, access_size);
-        data |= (tmp & access_mask) << (i * 8);
-    }
+    access_with_adjusted_size(addr + mr->offset, &data, size,
+                              mr->ops->impl.min_access_size,
+                              mr->ops->impl.max_access_size,
+                              memory_region_read_accessor, mr);
 
     return data;
 }
@@ -785,9 +828,6 @@ static void memory_region_write_thunk_n(void *_mr,
                                         uint64_t data)
 {
     MemoryRegion *mr = _mr;
-    unsigned access_size, access_size_min, access_size_max;
-    uint64_t access_mask;
-    unsigned i;
 
     if (!memory_region_access_valid(mr, addr, size)) {
         return; /* FIXME: better signalling */
@@ -799,23 +839,10 @@ static void memory_region_write_thunk_n(void *_mr,
     }
 
     /* FIXME: support unaligned access */
-
-    access_size_min = mr->ops->impl.min_access_size;
-    if (!access_size_min) {
-        access_size_min = 1;
-    }
-    access_size_max = mr->ops->impl.max_access_size;
-    if (!access_size_max) {
-        access_size_max = 4;
-    }
-    access_size = MAX(MIN(size, access_size_max), access_size_min);
-    access_mask = -1ULL >> (64 - access_size * 8);
-    addr += mr->offset;
-    for (i = 0; i < size; i += access_size) {
-        /* FIXME: big-endian support */
-        mr->ops->write(mr->opaque, addr + i, (data >> (i * 8)) & access_mask,
-                       access_size);
-    }
+    access_with_adjusted_size(addr + mr->offset, &data, size,
+                              mr->ops->impl.min_access_size,
+                              mr->ops->impl.max_access_size,
+                              memory_region_write_accessor, mr);
 }
 
 static uint32_t memory_region_read_thunk_b(void *mr, target_phys_addr_t addr)