KVM: selftests: Ensure KVM supports AVX for SEV-ES VMSA FPU test

Verify that KVM's supported XCR0 includes AVX (and earlier features) when
running the SEV-ES VMSA XSAVE test.  In practice, the issue will likely
never pop up, since KVM support for AVX predates KVM support for SEV-ES,
but checking for KVM support makes the requirement more obvious.

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/20241003234337.273364-12-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

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

@@ -181,6 +181,8 @@ static void test_sev_es_shutdown(void)
 
 int main(int argc, char *argv[])
 {
+	const u64 xf_mask = XFEATURE_MASK_X87_AVX;
+
 	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_SEV));
 
 	test_sev(guest_sev_code, SEV_POLICY_NO_DBG);
@@ -193,7 +195,7 @@ int main(int argc, char *argv[])
 		test_sev_es_shutdown();
 
 		if (kvm_has_cap(KVM_CAP_XCRS) &&
-		    (xgetbv(0) & XFEATURE_MASK_X87_AVX) == XFEATURE_MASK_X87_AVX) {
+		    (xgetbv(0) & kvm_cpu_supported_xcr0() & xf_mask) == xf_mask) {
 			test_sync_vmsa(0);
 			test_sync_vmsa(SEV_POLICY_NO_DBG);
 		}