Better max VMCS field index test

index 5803dc7..a1af59c 100644
@@ -348,6 +348,34 @@ static bool check_all_vmcs_fields(u8 cookie)
 	return __check_all_vmcs_fields(cookie, NULL);
 }
 
+static u32 find_vmcs_max_index(void)
+{
+	u32 idx, width, type, enc;
+	u64 actual;
+	int ret;
+
+	/* scan backwards and stop when found */
+	for (idx = (1 << 9) - 1; idx >= 0; idx--) {
+
+		/* try all combinations of width and type */
+		for (type = 0; type < (1 << 2); type++) {
+			for (width = 0; width < (1 << 2) ; width++) {
+				enc = (idx << VMCS_FIELD_INDEX_SHIFT) |
+				      (type << VMCS_FIELD_TYPE_SHIFT) |
+				      (width << VMCS_FIELD_WIDTH_SHIFT);
+
+				ret = vmcs_read_checking(enc, &actual);
+				assert(!(ret & X86_EFLAGS_CF));
+				if (!(ret & X86_EFLAGS_ZF))
+					return idx;
+			}
+		}
+	}
+	/* some VMCS fields should exist */
+	assert(0);
+	return 0;
+}
+
 static void test_vmwrite_vmread(void)
 {
 	struct vmcs *vmcs = alloc_page();

@@ -358,11 +386,13 @@ static void test_vmwrite_vmread(void)
 	assert(!make_vmcs_current(vmcs));
 
 	set_all_vmcs_fields(0x42);
-	report(__check_all_vmcs_fields(0x42, &max_index), "VMWRITE/VMREAD");
+	report(check_all_vmcs_fields(0x42), "VMWRITE/VMREAD");
 
-	vmcs_enum_max = rdmsr(MSR_IA32_VMX_VMCS_ENUM) & VMCS_FIELD_INDEX_MASK;
-	report(vmcs_enum_max >= max_index,
-	       "VMX_VMCS_ENUM.MAX_INDEX expected at least: %x, actual: %x",
+	vmcs_enum_max = (rdmsr(MSR_IA32_VMX_VMCS_ENUM) & VMCS_FIELD_INDEX_MASK)
+			>> VMCS_FIELD_INDEX_SHIFT;
+	max_index = find_vmcs_max_index();
+	report(vmcs_enum_max == max_index,
+	       "VMX_VMCS_ENUM.MAX_INDEX expected: %x, actual: %x",
 	       max_index, vmcs_enum_max);
 
 	assert(!vmcs_clear(vmcs));

index a1af59c..8bcb438 100644
@@ -281,11 +281,10 @@ static void set_vmcs_field(struct vmcs_field *f, u8 cookie)
 	vmcs_write(f->encoding, vmcs_field_value(f, cookie));
 }
 
-static bool check_vmcs_field(struct vmcs_field *f, u8 cookie, u32 *max_index)
+static bool check_vmcs_field(struct vmcs_field *f, u8 cookie)
 {
 	u64 expected;
 	u64 actual;
-	u32 index;
 	int ret;
 
 	if (f->encoding == VMX_INST_ERROR) {

@@ -299,12 +298,6 @@ static bool check_vmcs_field(struct vmcs_field *f, u8 cookie, u32 *max_index)
 	if (ret & X86_EFLAGS_ZF)
 		return true;
 
-	if (max_index) {
-		index = f->encoding & VMCS_FIELD_INDEX_MASK;
-		if (index > *max_index)
-			*max_index = index;
-	}
-
 	if (vmcs_field_readonly(f)) {
 		printf("Skipping read-only field %lx\n", f->encoding);
 		return true;

@@ -330,24 +323,19 @@ static void set_all_vmcs_fields(u8 cookie)
 		set_vmcs_field(&vmcs_fields[i], cookie);
 }
 
-static bool __check_all_vmcs_fields(u8 cookie, u32 *max_index)
+static bool check_all_vmcs_fields(u8 cookie)
 {
 	bool pass = true;
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(vmcs_fields); i++) {
-		if (!check_vmcs_field(&vmcs_fields[i], cookie, max_index))
+		if (!check_vmcs_field(&vmcs_fields[i], cookie))
 			pass = false;
 	}
 
 	return pass;
 }
 
-static bool check_all_vmcs_fields(u8 cookie)
-{
-	return __check_all_vmcs_fields(cookie, NULL);
-}
-
 static u32 find_vmcs_max_index(void)
 {
 	u32 idx, width, type, enc;