diff --git a/hw/milkymist-ac97.c b/hw/milkymist-ac97.c
index 6104732f7d..5c5ed275b3 100644
--- a/hw/milkymist-ac97.c
+++ b/hw/milkymist-ac97.c
@@ -53,6 +53,7 @@ enum {
 
 struct MilkymistAC97State {
     SysBusDevice busdev;
+    MemoryRegion regs_region;
 
     QEMUSoundCard card;
     SWVoiceIn *voice_in;
@@ -82,7 +83,8 @@ static void update_voices(MilkymistAC97State *s)
     }
 }
 
-static uint32_t ac97_read(void *opaque, target_phys_addr_t addr)
+static uint64_t ac97_read(void *opaque, target_phys_addr_t addr,
+                          unsigned size)
 {
     MilkymistAC97State *s = opaque;
     uint32_t r = 0;
@@ -113,7 +115,8 @@ static uint32_t ac97_read(void *opaque, target_phys_addr_t addr)
     return r;
 }
 
-static void ac97_write(void *opaque, target_phys_addr_t addr, uint32_t value)
+static void ac97_write(void *opaque, target_phys_addr_t addr, uint64_t value,
+                       unsigned size)
 {
     MilkymistAC97State *s = opaque;
 
@@ -159,16 +162,14 @@ static void ac97_write(void *opaque, target_phys_addr_t addr, uint32_t value)
 
 }
 
-static CPUReadMemoryFunc * const ac97_read_fn[] = {
-    NULL,
-    NULL,
-    &ac97_read,
-};
-
-static CPUWriteMemoryFunc * const ac97_write_fn[] = {
-    NULL,
-    NULL,
-    &ac97_write,
+static const MemoryRegionOps ac97_mmio_ops = {
+    .read = ac97_read,
+    .write = ac97_write,
+    .valid = {
+        .min_access_size = 4,
+        .max_access_size = 4,
+    },
+    .endianness = DEVICE_NATIVE_ENDIAN,
 };
 
 static void ac97_in_cb(void *opaque, int avail_b)
@@ -280,7 +281,6 @@ static int ac97_post_load(void *opaque, int version_id)
 static int milkymist_ac97_init(SysBusDevice *dev)
 {
     MilkymistAC97State *s = FROM_SYSBUS(typeof(*s), dev);
-    int ac97_regs;
 
     struct audsettings as;
     sysbus_init_irq(dev, &s->crrequest_irq);
@@ -300,9 +300,9 @@ static int milkymist_ac97_init(SysBusDevice *dev)
     s->voice_out = AUD_open_out(&s->card, s->voice_out,
             "mm_ac97.out", s, ac97_out_cb, &as);
 
-    ac97_regs = cpu_register_io_memory(ac97_read_fn, ac97_write_fn, s,
-            DEVICE_NATIVE_ENDIAN);
-    sysbus_init_mmio(dev, R_MAX * 4, ac97_regs);
+    memory_region_init_io(&s->regs_region, &ac97_mmio_ops, s,
+            "milkymist-ac97", R_MAX * 4);
+    sysbus_init_mmio_region(dev, &s->regs_region);
 
     return 0;
 }