[PATCH RFC v2 09/50] KVM: selftests: Test rejection of memfd for resource_fd

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@xxxxxxxxxx>

Add test coverage verifying that passing an fd created via memfd_create
as a resource file fails with EOPNOTSUPP, because regular files do not
implement gmem_provider_ops. Only directory file descriptors representing
the mount root are supported as resource pools.

Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
---
 tools/testing/selftests/kvm/guest_memfd_test.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index 445396860d819..d62ae23256083 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -457,6 +457,27 @@ static void test_resource_fd_unsupported_fs(struct kvm_vm *vm)
 	close(file_fd);
 }
 
+static void test_resource_fd_memfd(struct kvm_vm *vm)
+{
+	int fd, file_fd;
+
+	/*
+	 * Passing an fd returned by memfd_create is rejected with EOPNOTSUPP
+	 * because regular files do not have gmem_provider_ops defined on their
+	 * f_op. Only directory FDs representing the mount root are supported
+	 * resource pools.
+	 */
+	file_fd = memfd_create("test_memfd", 0);
+	TEST_ASSERT(file_fd >= 0, "memfd_create failed");
+
+	fd = __vm_create_guest_memfd_resource(vm, page_size,
+					      GUEST_MEMFD_FLAG_USE_RESOURCE,
+					      file_fd);
+	TEST_ASSERT(fd < 0, "guest_memfd with memfd should fail");
+	TEST_ASSERT_EQ(errno, EOPNOTSUPP);
+	close(file_fd);
+}
+
 #define ____gmem_test(__test, __vm, __flags, __gmem_size, args...)	\
 do {									\
 	int fd = vm_create_guest_memfd(__vm, __gmem_size, __flags);	\
@@ -517,6 +538,7 @@ static void test_guest_memfd(unsigned long vm_type)
 
 	test_resource_fd_invalid(vm);
 	test_resource_fd_unsupported_fs(vm);
+	test_resource_fd_memfd(vm);
 
 	__test_guest_memfd(vm, 0);
 

-- 
2.56.0.257.gf7497c7d27-goog