diff --git a/arch/x86/mm/mmio-mod.c b/arch/x86/mm/mmio-mod.c
index 3adff7d..7f71884b 100644
--- a/arch/x86/mm/mmio-mod.c
+++ b/arch/x86/mm/mmio-mod.c
@@ -219,6 +219,11 @@ static void post(struct kmmio_probe *p, unsigned long condition,
 		BUG();
 	}
 
+	if (my_trace->phys == 0xfaafc000) {
+		pr_info("ZAJEC: got it\n");
+		set_ins_reg_val(my_reason->ip, regs, 0x13816666);
+	}
+
 	switch (my_reason->type) {
 	case REG_READ:
 		my_trace->value = get_ins_reg_val(my_reason->ip, regs);
diff --git a/arch/x86/mm/pf_in.c b/arch/x86/mm/pf_in.c
index 9f0614d..86449ed 100644
--- a/arch/x86/mm/pf_in.c
+++ b/arch/x86/mm/pf_in.c
@@ -461,6 +461,99 @@ err:
 	return 0;
 }
 
+static void set_reg_w32(int no, struct pt_regs *regs, u32 val)
+{
+	switch (no) {
+	case arg_AX:
+		regs->ax = val;
+		break;
+	case arg_BX:
+		regs->bx = val;
+		break;
+	case arg_CX:
+		regs->cx = val;
+		break;
+	case arg_DX:
+		regs->dx = val;
+		break;
+	case arg_SP:
+		regs->sp = val;
+		break;
+	case arg_BP:
+		regs->bp = val;
+		break;
+	case arg_SI:
+		regs->si = val;
+		break;
+	case arg_DI:
+		regs->di = val;
+		break;
+#ifdef __amd64__
+	case arg_R8:
+		regs->r8 = val;
+		break;
+	case arg_R9:
+		regs->r9 = val;
+		break;
+	case arg_R10:
+		regs->r10 = val;
+		break;
+	case arg_R11:
+		regs->r11 = val;
+		break;
+	case arg_R12:
+		regs->r12 = val;
+		break;
+	case arg_R13:
+		regs->r13 = val;
+		break;
+	case arg_R14:
+		regs->r14 = val;
+		break;
+	case arg_R15:
+		regs->r15 = val;
+		break;
+#endif
+	default:
+		printk(KERN_ERR "mmiotrace: Error reg no# %d\n", no);
+	}
+}
+
+void set_ins_reg_val(unsigned long ins_addr, struct pt_regs *regs, u32 val)
+{
+	unsigned int opcode;
+	int reg;
+	unsigned char *p;
+	struct prefix_bits prf;
+	int i;
+
+	p = (unsigned char *)ins_addr;
+	p += skip_prefix(p, &prf);
+	p += get_opcode(p, &opcode);
+	for (i = 0; i < ARRAY_SIZE(reg_rop); i++)
+		if (reg_rop[i] == opcode)
+			goto do_work;
+
+	for (i = 0; i < ARRAY_SIZE(reg_wop); i++)
+		if (reg_wop[i] == opcode)
+			goto do_work;
+
+	printk(KERN_ERR "mmiotrace: Not a register instruction, opcode "
+							"0x%02x\n", opcode);
+	return;
+
+do_work:
+	/* for STOS, source register is fixed */
+	if (opcode == 0xAA || opcode == 0xAB) {
+		reg = arg_AX;
+	} else {
+		unsigned char mod_rm = *p;
+		reg = ((mod_rm >> 3) & 0x7) | (prf.rexr << 3);
+	}
+
+	set_reg_w32(reg, regs, val);
+}
+
 unsigned long get_ins_imm_val(unsigned long ins_addr)
 {
 	unsigned int opcode;
diff --git a/arch/x86/mm/pf_in.h b/arch/x86/mm/pf_in.h
index e05341a..90b43ff 100644
--- a/arch/x86/mm/pf_in.h
+++ b/arch/x86/mm/pf_in.h
@@ -34,6 +34,7 @@ enum reason_type {
 enum reason_type get_ins_type(unsigned long ins_addr);
 unsigned int get_ins_mem_width(unsigned long ins_addr);
 unsigned long get_ins_reg_val(unsigned long ins_addr, struct pt_regs *regs);
+void set_ins_reg_val(unsigned long ins_addr, struct pt_regs *regs, u32 val);
 unsigned long get_ins_imm_val(unsigned long ins_addr);
 
 #endif /* __PF_H_ */