[PATCH 4/6] KVM: selftests: Add test coverage for guest_memfd without GUEST_MEMFD_FLAG_MMAP

Sean Christopherson
2025-09-26T16:31:28Z

From: Ackerley Tng <ackerleytng@google.com>

If a VM type supports KVM_CAP_GUEST_MEMFD_MMAP, the guest_memfd test will
run all test cases with GUEST_MEMFD_FLAG_MMAP set. This leaves the code
path for creating a non-mmap()-able guest_memfd on a VM that supports
mappable guest memfds untested.

Refactor the test to run the main test suite with a given set of flags.
Then, for VM types that support the mappable capability, invoke the test
suite twice: once with no flags, and once with GUEST_MEMFD_FLAG_MMAP
set.

This ensures both creation paths are properly exercised on capable VMs.

test_guest_memfd_flags() tests valid flags, hence it can be run just once
per VM type, and valid flag identification can be moved into the test
function.

Signed-off-by: Ackerley Tng <ackerleytng@google.com>
[sean: use double-underscores for the inner helper]
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
.../testing/selftests/kvm/guest_memfd_test.c | 30 ++++++++++++-------
1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index 60c6dec63490..5a50a28ce1fa 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -239,11 +239,16 @@ static void test_create_guest_memfd_multiple(struct kvm_vm *vm)
close(fd1);
}

-static void test_guest_memfd_flags(struct kvm_vm *vm, uint64_t valid_flags)
+static void test_guest_memfd_flags(struct kvm_vm *vm)
{
+ uint64_t valid_flags = 0;
uint64_t flag;
int fd;

+ if (vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_MMAP))
+ valid_flags |= GUEST_MEMFD_FLAG_MMAP |
+ GUEST_MEMFD_FLAG_DEFAULT_SHARED;
+
for (flag = BIT(0); flag; flag <<= 1) {
fd = __vm_create_guest_memfd(vm, page_size, flag);
if (flag & valid_flags) {
@@ -267,16 +272,8 @@ do { \
close(fd); \
} while (0)

-static void test_guest_memfd(unsigned long vm_type)
+static void __test_guest_memfd(struct kvm_vm *vm, uint64_t flags)
{
- uint64_t flags = 0;
- struct kvm_vm *vm;
-
- vm = vm_create_barebones_type(vm_type);
-
- if (vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_MMAP))
- flags |= GUEST_MEMFD_FLAG_MMAP | GUEST_MEMFD_FLAG_DEFAULT_SHARED;
-
test_create_guest_memfd_multiple(vm);
test_create_guest_memfd_invalid_sizes(vm, flags);

@@ -292,8 +289,19 @@ static void test_guest_memfd(unsigned long vm_type)
gmem_test(file_size, vm, flags);
gmem_test(fallocate, vm, flags);
gmem_test(invalid_punch_hole, vm, flags);
+}

- test_guest_memfd_flags(vm, flags);
+static void test_guest_memfd(unsigned long vm_type)
+{
+ struct kvm_vm *vm = vm_create_barebones_type(vm_type);
+
+ test_guest_memfd_flags(vm);
+
+ __test_guest_memfd(vm, 0);
+
+ if (vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_MMAP))
+ __test_guest_memfd(vm, GUEST_MEMFD_FLAG_MMAP |
+ GUEST_MEMFD_FLAG_DEFAULT_SHARED);

kvm_vm_free(vm);
}
--
2.51.0.536.g15c5d4f767-goog