selftests: kvm: s390: Add s390x ucontrol test suite with hpage test

Add test suite to validate the s390x architecture specific ucontrol KVM
interface.

Make use of the selftest test harness.

* uc_cap_hpage testcase verifies that a ucontrol VM cannot be run with
  hugepages.

To allow testing of the ucontrol interface the kernel needs a
non-default config containing CONFIG_KVM_S390_UCONTROL.
This config needs to be set to built-in (y) as this cannot be built as
module.

Signed-off-by: Christoph Schlameuss <[email protected]>
Reviewed-by: Janosch Frank <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Janosch Frank <[email protected]>
Message-ID: <[email protected]>

Author: schlac

tools/testing/selftests/kvm/.gitignore

@@ -5,3 +5,4 @@
 !*.h
 !*.S
 !*.sh
+!config

tools/testing/selftests/kvm/Makefile

@@ -186,6 +186,7 @@ TEST_GEN_PROGS_s390x += s390x/tprot
 TEST_GEN_PROGS_s390x += s390x/cmma_test
 TEST_GEN_PROGS_s390x += s390x/debug_test
 TEST_GEN_PROGS_s390x += s390x/shared_zeropage_test
+TEST_GEN_PROGS_s390x += s390x/ucontrol_test
 TEST_GEN_PROGS_s390x += demand_paging_test
 TEST_GEN_PROGS_s390x += dirty_log_test
 TEST_GEN_PROGS_s390x += guest_print_test

tools/testing/selftests/kvm/s390x/config

@@ -0,0 +1,2 @@
+CONFIG_KVM=y
+CONFIG_KVM_S390_UCONTROL=y

tools/testing/selftests/kvm/s390x/ucontrol_test.c

@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Test code for the s390x kvm ucontrol interface
+ *
+ * Copyright IBM Corp. 2024
+ *
+ * Authors:
+ *  Christoph Schlameuss <[email protected]>
+ */
+#include "kselftest_harness.h"
+#include "kvm_util.h"
+
+#include <linux/capability.h>
+#include <linux/sizes.h>
+
+/* so directly declare capget to check caps without libcap */
+int capget(cap_user_header_t header, cap_user_data_t data);
+
+/**
+ * In order to create user controlled virtual machines on S390,
+ * check KVM_CAP_S390_UCONTROL and use the flag KVM_VM_S390_UCONTROL
+ * as privileged user (SYS_ADMIN).
+ */
+void require_ucontrol_admin(void)
+{
+	struct __user_cap_data_struct data[_LINUX_CAPABILITY_U32S_3];
+	struct __user_cap_header_struct hdr = {
+		.version = _LINUX_CAPABILITY_VERSION_3,
+	};
+	int rc;
+
+	rc = capget(&hdr, data);
+	TEST_ASSERT_EQ(0, rc);
+	TEST_REQUIRE((data->effective & CAP_TO_MASK(CAP_SYS_ADMIN)) > 0);
+
+	TEST_REQUIRE(kvm_has_cap(KVM_CAP_S390_UCONTROL));
+}
+
+/**
+ * Assert HPAGE CAP cannot be enabled on UCONTROL VM
+ */
+TEST(uc_cap_hpage)
+{
+	int rc, kvm_fd, vm_fd, vcpu_fd;
+	struct kvm_enable_cap cap = {
+		.cap = KVM_CAP_S390_HPAGE_1M,
+	};
+
+	require_ucontrol_admin();
+
+	kvm_fd = open_kvm_dev_path_or_exit();
+	vm_fd = ioctl(kvm_fd, KVM_CREATE_VM, KVM_VM_S390_UCONTROL);
+	ASSERT_GE(vm_fd, 0);
+
+	/* assert hpages are not supported on ucontrol vm */
+	rc = ioctl(vm_fd, KVM_CHECK_EXTENSION, KVM_CAP_S390_HPAGE_1M);
+	EXPECT_EQ(0, rc);
+
+	/* Test that KVM_CAP_S390_HPAGE_1M can't be enabled for a ucontrol vm */
+	rc = ioctl(vm_fd, KVM_ENABLE_CAP, cap);
+	EXPECT_EQ(-1, rc);
+	EXPECT_EQ(EINVAL, errno);
+
+	/* assert HPAGE CAP is rejected after vCPU creation */
+	vcpu_fd = ioctl(vm_fd, KVM_CREATE_VCPU, 0);
+	ASSERT_GE(vcpu_fd, 0);
+	rc = ioctl(vm_fd, KVM_ENABLE_CAP, cap);
+	EXPECT_EQ(-1, rc);
+	EXPECT_EQ(EBUSY, errno);
+
+	close(vcpu_fd);
+	close(vm_fd);
+	close(kvm_fd);
+}
+
+TEST_HARNESS_MAIN