KVM: selftests: hyperv_cpuid: add check for NoNonArchitecturalCoreSharing bit

The bit is supposed to be '1' when SMT is not supported or forcefully
disabled and '0' otherwise.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/x86_64/hyperv_cpuid.c

@@ -26,6 +26,25 @@ static void guest_code(void)
 {
 }
 
+static int smt_possible(void)
+{
+	char buf[16];
+	FILE *f;
+	bool res = 1;
+
+	f = fopen("/sys/devices/system/cpu/smt/control", "r");
+	if (f) {
+		if (fread(buf, sizeof(*buf), sizeof(buf), f) > 0) {
+			if (!strncmp(buf, "forceoff", 8) ||
+			    !strncmp(buf, "notsupported", 12))
+				res = 0;
+		}
+		fclose(f);
+	}
+
+	return res;
+}
+
 static void test_hv_cpuid(struct kvm_cpuid2 *hv_cpuid_entries,
 			  int evmcs_enabled)
 {
@@ -59,6 +78,14 @@ static void test_hv_cpuid(struct kvm_cpuid2 *hv_cpuid_entries,
 		TEST_ASSERT(!entry->padding[0] && !entry->padding[1] &&
 			    !entry->padding[2], "padding should be zero");
 
+		if (entry->function == 0x40000004) {
+			int nononarchcs = !!(entry->eax & (1UL << 18));
+
+			TEST_ASSERT(nononarchcs == !smt_possible(),
+				    "NoNonArchitecturalCoreSharing bit"
+				    " doesn't reflect SMT setting");
+		}
+
 		/*
 		 * If needed for debug:
 		 * fprintf(stdout,