diff --git a/hw/pckbd.c b/hw/pckbd.c
index 52b65d7d93..de508b3090 100644
--- a/hw/pckbd.c
+++ b/hw/pckbd.c
@@ -125,6 +125,7 @@ typedef struct KBDState {
     qemu_irq irq_kbd;
     qemu_irq irq_mouse;
     target_phys_addr_t base;
+    int it_shift;
 } KBDState;
 
 KBDState kbd_state;
@@ -384,21 +385,28 @@ uint32_t kbd_mm_readb (void *opaque, target_phys_addr_t addr)
 {
     KBDState *s = opaque;
 
-    if (addr == s->base)
-        return kbd_read_data(s, 0);
-    else
-        return kbd_read_status(s, 0);
+    switch ((addr - s->base) >> s->it_shift) {
+    case 0:
+        return kbd_read_data(s, 0) & 0xff;
+    case 1:
+        return kbd_read_status(s, 0) & 0xff;
+    default:
+        return 0xff;
+    }
 }
 
-void kbd_mm_writeb (void *opaque,
-                       target_phys_addr_t addr, uint32_t value)
+void kbd_mm_writeb (void *opaque, target_phys_addr_t addr, uint32_t value)
 {
     KBDState *s = opaque;
 
-    if (addr == s->base)
-        kbd_write_data(s, 0, value);
-    else
-        kbd_write_command(s, 0, value);
+    switch ((addr - s->base) >> s->it_shift) {
+    case 0:
+        kbd_write_data(s, 0, value & 0xff);
+        break;
+    case 1:
+        kbd_write_command(s, 0, value & 0xff);
+        break;
+    }
 }
 
 static CPUReadMemoryFunc *kbd_mm_read[] = {
@@ -413,7 +421,8 @@ static CPUWriteMemoryFunc *kbd_mm_write[] = {
     &kbd_mm_writeb,
 };
 
-void i8042_mm_init(qemu_irq kbd_irq, qemu_irq mouse_irq, target_ulong base, int it_shift)
+void i8042_mm_init(qemu_irq kbd_irq, qemu_irq mouse_irq, target_ulong base,
+                   int it_shift)
 {
     KBDState *s = &kbd_state;
     int s_io_memory;
@@ -421,11 +430,12 @@ void i8042_mm_init(qemu_irq kbd_irq, qemu_irq mouse_irq, target_ulong base, int
     s->irq_kbd = kbd_irq;
     s->irq_mouse = mouse_irq;
     s->base = base;
+    s->it_shift = it_shift;
 
     kbd_reset(s);
     register_savevm("pckbd", 0, 3, kbd_save, kbd_load, s);
     s_io_memory = cpu_register_io_memory(0, kbd_mm_read, kbd_mm_write, s);
-    cpu_register_physical_memory(base & ~(TARGET_PAGE_SIZE - 1), TARGET_PAGE_SIZE, s_io_memory);
+    cpu_register_physical_memory(base, 8 << it_shift, s_io_memory);
 
     s->kbd = ps2_kbd_init(kbd_update_kbd_irq, s);
     s->mouse = ps2_mouse_init(kbd_update_aux_irq, s);