[PATCH v2 08/13] KVM: selftests: Add test coverage for guest_memfd without GUEST_MEMFD_FLAG_MMAP

Sean Christopherson
2025-10-03T23:26:26Z

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.

Run test_guest_memfd_flags() only once per VM type since it depends only
on the set of valid/supported flags, i.e. iterating over an arbitrary set
of flags is both unnecessary and wrong.

Signed-off-by: Ackerley Tng <ackerleytng@google.com>
[sean: use double-underscores for the inner helper]
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
.../testing/selftests/kvm/guest_memfd_test.c | 27 +++++++++++--------
1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index afdc4d3a956d..9f98a067ab51 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -268,18 +268,8 @@ 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)
{
- struct kvm_vm *vm;
- uint64_t flags;
-
- vm = vm_create_barebones_type(vm_type);
- flags = vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_FLAGS);
-
- /* This test doesn't yet support testing mmap() on private memory. */
- if (!(flags & GUEST_MEMFD_FLAG_INIT_SHARED))
- flags &= ~GUEST_MEMFD_FLAG_MMAP;
-
test_create_guest_memfd_multiple(vm);
test_create_guest_memfd_invalid_sizes(vm, flags);

@@ -295,9 +285,24 @@ 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);
+}
+
+static void test_guest_memfd(unsigned long vm_type)
+{
+ struct kvm_vm *vm = vm_create_barebones_type(vm_type);
+ uint64_t flags;

test_guest_memfd_flags(vm);

+ __test_guest_memfd(vm, 0);
+
+ flags = vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_FLAGS);
+
+ /* MMAP should always be supported if INIT_SHARED is supported. */
+ if (flags & GUEST_MEMFD_FLAG_INIT_SHARED)
+ __test_guest_memfd(vm, GUEST_MEMFD_FLAG_MMAP |
+ GUEST_MEMFD_FLAG_INIT_SHARED);
+
kvm_vm_free(vm);
}

--
2.51.0.618.g983fd99d29-goog