selftests: kvm: check dynamic bits against KVM_X86_XCOMP_GUEST_SUPP

Provide coverage for the new API.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/arch/x86/include/uapi/asm/kvm.h

@@ -452,6 +452,9 @@ struct kvm_sync_regs {
 
 #define KVM_STATE_VMX_PREEMPTION_TIMER_DEADLINE	0x00000001
 
+/* attributes for system fd (group 0) */
+#define KVM_X86_XCOMP_GUEST_SUPP	0
+
 struct kvm_vmx_nested_state_data {
 	__u8 vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
 	__u8 shadow_vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];

tools/include/uapi/linux/kvm.h

@@ -1133,6 +1133,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM 206
 #define KVM_CAP_VM_GPA_BITS 207
 #define KVM_CAP_XSAVE2 208
+#define KVM_CAP_SYS_ATTRIBUTES 209
 
 #ifdef KVM_CAP_IRQ_ROUTING
 

tools/testing/selftests/kvm/lib/x86_64/processor.c

@@ -667,8 +667,23 @@ static bool is_xfd_supported(void)
 
 void vm_xsave_req_perm(int bit)
 {
+	int kvm_fd;
 	u64 bitmask;
 	long rc;
+	struct kvm_device_attr attr = {
+		.group = 0,
+		.attr = KVM_X86_XCOMP_GUEST_SUPP,
+		.addr = (unsigned long) &bitmask
+	};
+
+	kvm_fd = open_kvm_dev_path_or_exit();
+	rc = ioctl(kvm_fd, KVM_GET_DEVICE_ATTR, &attr);
+	close(kvm_fd);
+	if (rc == -1 && (errno == ENXIO || errno == EINVAL))
+		exit(KSFT_SKIP);
+	TEST_ASSERT(rc == 0, "KVM_GET_DEVICE_ATTR(0, KVM_X86_XCOMP_GUEST_SUPP) error: %ld", rc);
+	if (!(bitmask & (1ULL << bit)))
+		exit(KSFT_SKIP);
 
 	if (!is_xfd_supported())
 		exit(KSFT_SKIP);