KVM: selftests: Add test coverage for guest_memfd without GUEST_MEMFD_FLAG_MMAP

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>
Link: https://lore.kernel.org/r/20251003232606.4070510-9-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index afdc4d3a956d67df307059639546423aa4ca9f3f..9f98a067ab51862bdf80fd2dde8245ac5e6ef43c 100644 (file)
--- 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);
 }