[RFC PATCH 03/11] KVM: selftests: Add tests for KVM_LINK_GUEST_MEMFD ioctl

[Ackerley Tng <ackerleytng@google.com>]

Test that

+ Invalid inputs should be rejected with EINVAL
+ Successful inputs return a new (destination) fd
+ Destination and source fds have the same inode number
+ No crash on program exit

Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 .../testing/selftests/kvm/guest_memfd_test.c  | 42 +++++++++++++++++++
 .../selftests/kvm/include/kvm_util_base.h     | 18 ++++++++
 2 files changed, 60 insertions(+)

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index ad20f11b2d2c..38fe96ea60f9 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -105,6 +105,47 @@ static void test_create_guest_memfd_invalid(struct kvm_vm *vm, size_t page_size)
 	ASSERT_EQ(errno, EINVAL);
 }
 
+static void test_link(struct kvm_vm *src_vm, int src_fd, size_t total_size)
+{
+	int ret;
+	int dst_fd;
+	struct kvm_vm *dst_vm;
+	struct stat src_stat;
+	struct stat dst_stat;
+
+	dst_vm = vm_create_barebones();
+
+	/* Linking with a nonexistent fd */
+	dst_fd = __vm_link_guest_memfd(dst_vm, 99, 0);
+	ASSERT_EQ(dst_fd, -1);
+	ASSERT_EQ(errno, EINVAL);
+
+	/* Linking with a non-gmem fd */
+	dst_fd = __vm_link_guest_memfd(dst_vm, 0, 1);
+	ASSERT_EQ(dst_fd, -1);
+	ASSERT_EQ(errno, EINVAL);
+
+	/* Linking with invalid flags */
+	dst_fd = __vm_link_guest_memfd(dst_vm, src_fd, 1);
+	ASSERT_EQ(dst_fd, -1);
+	ASSERT_EQ(errno, EINVAL);
+
+	/* Linking with an already-associated vm */
+	dst_fd = __vm_link_guest_memfd(src_vm, src_fd, 1);
+	ASSERT_EQ(dst_fd, -1);
+	ASSERT_EQ(errno, EINVAL);
+
+	dst_fd = __vm_link_guest_memfd(dst_vm, src_fd, 0);
+	TEST_ASSERT(dst_vm > 0, "linking should succeed with valid inputs");
+	TEST_ASSERT(src_fd != dst_fd, "linking should return a different fd");
+
+	ret = fstat(src_fd, &src_stat);
+	ASSERT_EQ(ret, 0);
+	ret = fstat(dst_fd, &dst_stat);
+	ASSERT_EQ(ret, 0);
+	TEST_ASSERT(src_stat.st_ino == dst_stat.st_ino,
+		    "src and dst files should have the same inode number");
+}
 
 int main(int argc, char *argv[])
 {
@@ -126,6 +167,7 @@ int main(int argc, char *argv[])
 	test_mmap(fd, page_size);
 	test_file_size(fd, page_size, total_size);
 	test_fallocate(fd, page_size, total_size);
+	test_link(vm, fd, total_size);
 
 	close(fd);
 }
diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
index 8bdfadd72349..868925b26a7b 100644
--- a/tools/testing/selftests/kvm/include/kvm_util_base.h
+++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
@@ -495,6 +495,24 @@ static inline int vm_create_guest_memfd(struct kvm_vm *vm, uint64_t size,
 	return fd;
 }
 
+static inline int __vm_link_guest_memfd(struct kvm_vm *vm, int fd, uint64_t flags)
+{
+	struct kvm_link_guest_memfd params = {
+		.fd = fd,
+		.flags = flags,
+	};
+
+	return __vm_ioctl(vm, KVM_LINK_GUEST_MEMFD, &params);
+}
+
+static inline int vm_link_guest_memfd(struct kvm_vm *vm, int fd, uint64_t flags)
+{
+	int new_fd = __vm_link_guest_memfd(vm, fd, flags);
+
+	TEST_ASSERT(new_fd >= 0, KVM_IOCTL_ERROR(KVM_LINK_GUEST_MEMFD, new_fd));
+	return new_fd;
+}
+
 void vm_set_user_memory_region(struct kvm_vm *vm, uint32_t slot, uint32_t flags,
 			       uint64_t gpa, uint64_t size, void *hva);
 int __vm_set_user_memory_region(struct kvm_vm *vm, uint32_t slot, uint32_t flags,
-- 
2.41.0.640.ga95def55d0-goog