--- .before/arch/x86/kvm/x86.c	2010-06-13 15:01:29.000000000 +0300
+++ .after/arch/x86/kvm/x86.c	2010-06-13 15:01:29.000000000 +0300
@@ -3286,13 +3286,14 @@ static int kvm_fetch_guest_virt(gva_t ad
 					  access | PFERR_FETCH_MASK, error);
 }
 
-static int kvm_read_guest_virt(gva_t addr, void *val, unsigned int bytes,
+int kvm_read_guest_virt(gva_t addr, void *val, unsigned int bytes,
 			       struct kvm_vcpu *vcpu, u32 *error)
 {
 	u32 access = (kvm_x86_ops->get_cpl(vcpu) == 3) ? PFERR_USER_MASK : 0;
 	return kvm_read_guest_virt_helper(addr, val, bytes, vcpu, access,
 					  error);
 }
+EXPORT_SYMBOL_GPL(kvm_read_guest_virt);
 
 static int kvm_read_guest_virt_system(gva_t addr, void *val, unsigned int bytes,
 			       struct kvm_vcpu *vcpu, u32 *error)
--- .before/arch/x86/kvm/x86.h	2010-06-13 15:01:29.000000000 +0300
+++ .after/arch/x86/kvm/x86.h	2010-06-13 15:01:29.000000000 +0300
@@ -75,6 +75,9 @@ static inline struct kvm_mem_aliases *kv
 void kvm_before_handle_nmi(struct kvm_vcpu *vcpu);
 void kvm_after_handle_nmi(struct kvm_vcpu *vcpu);
 
+int kvm_read_guest_virt(gva_t addr, void *val, unsigned int bytes,
+			struct kvm_vcpu *vcpu, u32 *error);
+
 extern int nested;
 
 #endif
--- .before/arch/x86/kvm/vmx.c	2010-06-13 15:01:29.000000000 +0300
+++ .after/arch/x86/kvm/vmx.c	2010-06-13 15:01:29.000000000 +0300
@@ -3654,6 +3654,86 @@ static int handle_vmoff(struct kvm_vcpu 
 	return 1;
 }
 
+/*
+ * Decode the memory-address operand of a vmx instruction, according to the
+ * Intel spec.
+ */
+#define VMX_OPERAND_SCALING(vii)	((vii) & 3)
+#define VMX_OPERAND_ADDR_SIZE(vii)	(((vii) >> 7) & 7)
+#define VMX_OPERAND_IS_REG(vii)		((vii) & (1u << 10))
+#define VMX_OPERAND_SEG_REG(vii)	(((vii) >> 15) & 7)
+#define VMX_OPERAND_INDEX_REG(vii)	(((vii) >> 18) & 0xf)
+#define VMX_OPERAND_INDEX_INVALID(vii)	((vii) & (1u << 22))
+#define VMX_OPERAND_BASE_REG(vii)	(((vii) >> 23) & 0xf)
+#define VMX_OPERAND_BASE_INVALID(vii)	((vii) & (1u << 27))
+#define VMX_OPERAND_REG(vii)		(((vii) >> 3) & 0xf)
+#define VMX_OPERAND_REG2(vii)		(((vii) >> 28) & 0xf)
+static gva_t get_vmx_mem_address(struct kvm_vcpu *vcpu,
+				 unsigned long exit_qualification,
+				 u32 vmx_instruction_info)
+{
+	int  scaling = VMX_OPERAND_SCALING(vmx_instruction_info);
+	int  addr_size = VMX_OPERAND_ADDR_SIZE(vmx_instruction_info);
+	bool is_reg = VMX_OPERAND_IS_REG(vmx_instruction_info);
+	int  seg_reg = VMX_OPERAND_SEG_REG(vmx_instruction_info);
+	int  index_reg = VMX_OPERAND_SEG_REG(vmx_instruction_info);
+	bool index_is_valid = !VMX_OPERAND_INDEX_INVALID(vmx_instruction_info);
+	int  base_reg       = VMX_OPERAND_BASE_REG(vmx_instruction_info);
+	bool base_is_valid  = !VMX_OPERAND_BASE_INVALID(vmx_instruction_info);
+	gva_t addr;
+
+	if (is_reg) {
+		kvm_queue_exception(vcpu, UD_VECTOR);
+		return 0;
+	}
+
+	switch (addr_size) {
+	case 1: /* 32 bit. high bits are undefined according to the spec: */
+		exit_qualification &= 0xffffffff;
+		break;
+	case 2: /* 64 bit */
+		break;
+	default: /* addr_size=0 means 16 bit */
+		return 0;
+	}
+
+	/* Addr = segment_base + offset */
+	/* offfset = Base + [Index * Scale] + Displacement */
+	addr = vmx_get_segment_base(vcpu, seg_reg);
+	if (base_is_valid)
+		addr += kvm_register_read(vcpu, base_reg);
+	if (index_is_valid)
+		addr += kvm_register_read(vcpu, index_reg)<<scaling;
+	addr += exit_qualification; /* holds the displacement */
+
+	return addr;
+}
+
+static int read_guest_vmcs_gpa(struct kvm_vcpu *vcpu, gpa_t *gpap)
+{
+	int r;
+	gva_t gva = get_vmx_mem_address(vcpu,
+		vmcs_readl(EXIT_QUALIFICATION),
+		vmcs_read32(VMX_INSTRUCTION_INFO));
+	if (gva == 0)
+		return 1;
+	*gpap = 0;
+	r = kvm_read_guest_virt(gva, gpap, sizeof(*gpap), vcpu, NULL);
+	if (r) {
+		printk(KERN_ERR "%s cannot read guest vmcs addr %lx : %d\n",
+		       __func__, gva, r);
+		return r;
+	}
+	/* According to the spec, VMCS addresses must be 4K aligned */
+	if (!IS_ALIGNED(*gpap, PAGE_SIZE)) {
+		printk(KERN_DEBUG "%s addr %llx not aligned\n",
+		       __func__, *gpap);
+		return 1;
+	}
+
+	return 0;
+}
+
 static int handle_invlpg(struct kvm_vcpu *vcpu)
 {
 	unsigned long exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
