[kvm-unit-tests PATCH] x86: VMX: Check preconditions for RDTSC test

[Oliver Upton <oupton@google.com>]

The RDTSC VM-exit test requires the 'use TSC offsetting' processor-based
VM-execution control be allowed on the host. Check this precondition
before running the test rather than asserting it later on to avoid
erroneous failures on a host without TSC offsetting.

Cc: Aaron Lewis <aaronlewis@google.com>
Signed-off-by: Oliver Upton <oupton@google.com>
---
 x86/vmx_tests.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
index 3b150323b325..de9a931216e2 100644
--- a/x86/vmx_tests.c
+++ b/x86/vmx_tests.c
@@ -9161,9 +9161,6 @@ static void vmx_vmcs_shadow_test(void)
  */
 static void reset_guest_tsc_to_zero(void)
 {
-	TEST_ASSERT_MSG(ctrl_cpu_rev[0].clr & CPU_USE_TSC_OFFSET,
-			"Expected support for 'use TSC offsetting'");
-
 	vmcs_set_bits(CPU_EXEC_CTRL0, CPU_USE_TSC_OFFSET);
 	vmcs_write(TSC_OFFSET, -rdtsc());
 }
@@ -9210,6 +9207,11 @@ static void rdtsc_vmexit_diff_test(void)
 	int fail = 0;
 	int i;
 
+	if (!(ctrl_cpu_rev[0].clr & CPU_USE_TSC_OFFSET)) {
+		printf("CPU doesn't support the 'use TSC offsetting' processor-based VM-execution control.\n");
+		return;
+	}
+
 	test_set_guest(rdtsc_vmexit_diff_test_guest);
 
 	reset_guest_tsc_to_zero();
-- 
2.25.0.341.g760bfbb309-goog