linux-kernel - [RFC PATCH v2 05/13] KVM: selftests: Add tests for KVM_LINK_GUEST

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Message-ID: <1ade7750adbfe39ca5b8e074ad5edb37a7bc7e54.1747368092.git.afranji@google.com>
Date: Fri, 16 May 2025 19:19:25 +0000
From: Ryan Afranji <afranji@...gle.com>
To: afranji@...gle.com, ackerleytng@...gle.com, pbonzini@...hat.com, 
	seanjc@...gle.com, tglx@...utronix.de, x86@...nel.org, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	tabba@...gle.com
Cc: mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com, 
	shuah@...nel.org, andrew.jones@...ux.dev, ricarkol@...gle.com, 
	chao.p.peng@...ux.intel.com, jarkko@...nel.org, yu.c.zhang@...ux.intel.com, 
	vannapurve@...gle.com, erdemaktas@...gle.com, mail@...iej.szmigiero.name, 
	vbabka@...e.cz, david@...hat.com, qperret@...gle.com, michael.roth@....com, 
	wei.w.wang@...el.com, liam.merwick@...cle.com, isaku.yamahata@...il.com, 
	kirill.shutemov@...ux.intel.com, sagis@...gle.com, jthoughton@...gle.com
Subject: [RFC PATCH v2 05/13] KVM: selftests: Add tests for
 KVM_LINK_GUEST_MEMFD ioctl

From: Ackerley Tng <ackerleytng@...gle.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@...gle.com>
Signed-off-by: Ryan Afranji <afranji@...gle.com>
---
 .../testing/selftests/kvm/guest_memfd_test.c  | 43 +++++++++++++++++++
 .../testing/selftests/kvm/include/kvm_util.h  | 18 ++++++++
 2 files changed, 61 insertions(+)

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index ce687f8d248f..9b2a58cd9b64 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -170,6 +170,48 @@ static void test_create_guest_memfd_multiple(struct kvm_vm *vm)
 	close(fd1);
 }
 
+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);
+	TEST_ASSERT_EQ(dst_fd, -1);
+	TEST_ASSERT_EQ(errno, EINVAL);
+
+	/* Linking with a non-gmem fd */
+	dst_fd = __vm_link_guest_memfd(dst_vm, 0, 1);
+	TEST_ASSERT_EQ(dst_fd, -1);
+	TEST_ASSERT_EQ(errno, EINVAL);
+
+	/* Linking with invalid flags */
+	dst_fd = __vm_link_guest_memfd(dst_vm, src_fd, 1);
+	TEST_ASSERT_EQ(dst_fd, -1);
+	TEST_ASSERT_EQ(errno, EINVAL);
+
+	/* Linking with an already-associated vm */
+	dst_fd = __vm_link_guest_memfd(src_vm, src_fd, 1);
+	TEST_ASSERT_EQ(dst_fd, -1);
+	TEST_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);
+	TEST_ASSERT_EQ(ret, 0);
+	ret = fstat(dst_fd, &dst_stat);
+	TEST_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[])
 {
 	size_t page_size;
@@ -194,6 +236,7 @@ int main(int argc, char *argv[])
 	test_file_size(fd, page_size, total_size);
 	test_fallocate(fd, page_size, total_size);
 	test_invalid_punch_hole(fd, page_size, total_size);
+	test_link(vm, fd, total_size);
 
 	close(fd);
 }
diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 373912464fb4..68faa658b69e 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -571,6 +571,24 @@ 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,
-- 
2.49.0.1101.gccaa498523-goog