Index: sys/dev/acpica/Osd/OsdMemory.c
===================================================================
--- sys/dev/acpica/Osd/OsdMemory.c	(revision 243380)
+++ sys/dev/acpica/Osd/OsdMemory.c	(working copy)
@@ -40,6 +40,45 @@ __FBSDID("$FreeBSD$");
 #include <vm/vm.h>
 #include <vm/pmap.h>
 
+#if defined(__amd64__) || defined(__i386__)
+#define	READ8(p, v)				\
+    __asm __volatile("movzbl %1, %%eax" : "=a" (v) : "m" (*(uint8_t *)(p)))
+#define	READ16(p, v)				\
+    __asm __volatile("movzwl %1, %%eax" : "=a" (v) : "m" (*(uint16_t *)(p)))
+#define	READ32(p, v)				\
+    __asm __volatile("movl %1, %%eax" : "=a" (v) : "m" (*(uint32_t *)(p)))
+#define	READ64(p, v)	do {			\
+	uint32_t l, u;				\
+						\
+	READ32(p, l);				\
+	READ32((uint32_t *)(p) + 1, u);		\
+	v = (uint64_t)l | ((uint64_t)u << 32);	\
+} while (0)
+#define	WRITE8(p, v)				\
+    __asm __volatile("movb %%al, %0" : "=m" (*(uint8_t *)(p)) : "a" (v))
+#define	WRITE16(p, v)				\
+    __asm __volatile("movw %%ax, %0" : "=m" (*(uint16_t *)(p)) : "a" (v))
+#define	WRITE32(p, v)				\
+    __asm __volatile("movl %%eax, %0" : "=m" (*(uint32_t *)(p)) : "a" (v))
+#define	WRITE64(p, v)	do {			\
+	uint32_t l, u;				\
+						\
+	l = (v) & 0xffffffff;			\
+	u = ((v) >> 32) & 0xffffffff;		\
+	WRITE32(p, l);				\
+	WRITE32((uint32_t *)(p) + 1, u);	\
+} while (0)
+#else
+#define	READ8(p, v)	do { v = *(volatile uint8_t *)(p); } while (0)
+#define	READ16(p, v)	do { v = *(volatile uint16_t *)(p); } while (0)
+#define	READ32(p, v)	do { v = *(volatile uint32_t *)(p); } while (0)
+#define	READ64(p, v)	do { v = *(volatile uint64_t *)(p); } while (0)
+#define	WRITE8(p, v)	do { *(volatile uint8_t *)(p) = v; } while (0)
+#define	WRITE16(p, v)	do { *(volatile uint16_t *)(p) = v; } while (0)
+#define	WRITE32(p, v)	do { *(volatile uint32_t *)(p) = v; } while (0)
+#define	WRITE64(p, v)	do { *(volatile uint64_t *)(p) = v; } while (0)
+#endif
+
 static MALLOC_DEFINE(M_ACPICA, "acpica", "ACPI CA memory pool");
 
 void *
@@ -97,16 +136,16 @@ AcpiOsReadMemory(ACPI_PHYSICAL_ADDRESS Address, UI
 
     switch (Width) {
     case 8:
-	*Value = *(volatile uint8_t *)LogicalAddress;
+	READ8(LogicalAddress, *Value);
 	break;
     case 16:
-	*Value = *(volatile uint16_t *)LogicalAddress;
+	READ16(LogicalAddress, *Value);
 	break;
     case 32:
-	*Value = *(volatile uint32_t *)LogicalAddress;
+	READ32(LogicalAddress, *Value);
 	break;
     case 64:
-	*Value = *(volatile uint64_t *)LogicalAddress;
+	READ64(LogicalAddress, *Value);
 	break;
     }
 
@@ -126,16 +165,16 @@ AcpiOsWriteMemory(ACPI_PHYSICAL_ADDRESS Address, U
 
     switch (Width) {
     case 8:
-	*(volatile uint8_t *)LogicalAddress = Value;
+	WRITE8(LogicalAddress, Value);
 	break;
     case 16:
-	*(volatile uint16_t *)LogicalAddress = Value;
+	WRITE16(LogicalAddress, Value);
 	break;
     case 32:
-	*(volatile uint32_t *)LogicalAddress = Value;
+	WRITE32(LogicalAddress, Value);
 	break;
     case 64:
-	*(volatile uint64_t *)LogicalAddress = Value;
+	WRITE64(LogicalAddress, Value);
 	break;
     }