[kvm-unit-tests PATCH 1/2] x86: vmx: Comprehensive max VMCS field search

[Nadav Amit <namit@vmware.com>]

Search all VMCS fields when looking for the max VMCS field index.
Perform the search backwards to save some time. Change the existing test
to compare the maximum expected index (based on MSRs) is equal to the
actual one.  This improves the test that currently performs
greater-equal comparison.

Suggested-by: Jim Mattson <jmattson@google.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Nadav Amit <namit@vmware.com>
---
 x86/vmx.c | 38 ++++++++++++++++++++++++++++++++++----
 1 file changed, 34 insertions(+), 4 deletions(-)

diff --git a/x86/vmx.c b/x86/vmx.c
index 5803dc7..a1af59c 100644
--- a/x86/vmx.c
+++ b/x86/vmx.c
@@ -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));
-- 
2.17.1