KVM: selftests: Add test for uaccesses to non-existent vgic-v2 CPUIF

Assert that accesses to a non-existent vgic-v2 CPU interface
consistently fail across the various KVM device attr ioctls. This also
serves as a regression test for a bug wherein KVM hits a NULL
dereference when the CPUID specified in the ioctl is invalid.

Note that there is no need to print the observed errno, as TEST_ASSERT()
will take care of it.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240424173959.3776798-3-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

tools/testing/selftests/kvm/aarch64/vgic_init.c

@@ -84,6 +84,18 @@ static struct vm_gic vm_gic_create_with_vcpus(uint32_t gic_dev_type,
 	return v;
 }
 
+static struct vm_gic vm_gic_create_barebones(uint32_t gic_dev_type)
+{
+	struct vm_gic v;
+
+	v.gic_dev_type = gic_dev_type;
+	v.vm = vm_create_barebones();
+	v.gic_fd = kvm_create_device(v.vm, gic_dev_type);
+
+	return v;
+}
+
+
 static void vm_gic_destroy(struct vm_gic *v)
 {
 	close(v->gic_fd);
@@ -357,6 +369,40 @@ static void test_vcpus_then_vgic(uint32_t gic_dev_type)
 	vm_gic_destroy(&v);
 }
 
+#define KVM_VGIC_V2_ATTR(offset, cpu) \
+	(FIELD_PREP(KVM_DEV_ARM_VGIC_OFFSET_MASK, offset) | \
+	 FIELD_PREP(KVM_DEV_ARM_VGIC_CPUID_MASK, cpu))
+
+#define GIC_CPU_CTRL	0x00
+
+static void test_v2_uaccess_cpuif_no_vcpus(void)
+{
+	struct vm_gic v;
+	u64 val = 0;
+	int ret;
+
+	v = vm_gic_create_barebones(KVM_DEV_TYPE_ARM_VGIC_V2);
+	subtest_dist_rdist(&v);
+
+	ret = __kvm_has_device_attr(v.gic_fd, KVM_DEV_ARM_VGIC_GRP_CPU_REGS,
+				    KVM_VGIC_V2_ATTR(GIC_CPU_CTRL, 0));
+	TEST_ASSERT(ret && errno == EINVAL,
+		    "accessed non-existent CPU interface, want errno: %i",
+		    EINVAL);
+	ret = __kvm_device_attr_get(v.gic_fd, KVM_DEV_ARM_VGIC_GRP_CPU_REGS,
+				    KVM_VGIC_V2_ATTR(GIC_CPU_CTRL, 0), &val);
+	TEST_ASSERT(ret && errno == EINVAL,
+		    "accessed non-existent CPU interface, want errno: %i",
+		    EINVAL);
+	ret = __kvm_device_attr_set(v.gic_fd, KVM_DEV_ARM_VGIC_GRP_CPU_REGS,
+				    KVM_VGIC_V2_ATTR(GIC_CPU_CTRL, 0), &val);
+	TEST_ASSERT(ret && errno == EINVAL,
+		    "accessed non-existent CPU interface, want errno: %i",
+		    EINVAL);
+
+	vm_gic_destroy(&v);
+}
+
 static void test_v3_new_redist_regions(void)
 {
 	struct kvm_vcpu *vcpus[NR_VCPUS];
@@ -675,6 +721,9 @@ void run_tests(uint32_t gic_dev_type)
 	test_vcpus_then_vgic(gic_dev_type);
 	test_vgic_then_vcpus(gic_dev_type);
 
+	if (VGIC_DEV_IS_V2(gic_dev_type))
+		test_v2_uaccess_cpuif_no_vcpus();
+
 	if (VGIC_DEV_IS_V3(gic_dev_type)) {
 		test_v3_new_redist_regions();
 		test_v3_typer_accesses();