[RFC PATCH 34/39] KVM: selftests: Add notes in private_mem_kvm_exits_test for mmap-able guest_memfd

Ackerley Tng
2024-09-10T23:45:32Z

Note in comments why madvise() is not needed before setting memory to
private.

Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
.../selftests/kvm/x86_64/private_mem_kvm_exits_test.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86_64/private_mem_kvm_exits_test.c b/tools/testing/selftests/kvm/x86_64/private_mem_kvm_exits_test.c
index 13e72fcec8dd..f8bcfc897f6a 100644
--- a/tools/testing/selftests/kvm/x86_64/private_mem_kvm_exits_test.c
+++ b/tools/testing/selftests/kvm/x86_64/private_mem_kvm_exits_test.c
@@ -62,7 +62,11 @@ static void test_private_access_memslot_deleted(void)

virt_map(vm, EXITS_TEST_GVA, EXITS_TEST_GPA, EXITS_TEST_NPAGES);

- /* Request to access page privately */
+ /*
+ * Request to access page privately. madvise(MADV_DONTNEED) not required
+ * since memory was never mmap()-ed from guest_memfd. Anonymous memory
+ * was used instead for this memslot's userspace_addr.
+ */
vm_mem_set_private(vm, EXITS_TEST_GPA, EXITS_TEST_SIZE);

pthread_create(&vm_thread, NULL,
@@ -98,7 +102,10 @@ static void test_private_access_memslot_not_private(void)

virt_map(vm, EXITS_TEST_GVA, EXITS_TEST_GPA, EXITS_TEST_NPAGES);

- /* Request to access page privately */
+ /*
+ * Request to access page privately. madvise(MADV_DONTNEED) not required
+ * since the affected memslot doesn't use guest_memfd.
+ */
vm_mem_set_private(vm, EXITS_TEST_GPA, EXITS_TEST_SIZE);

exit_reason = run_vcpu_get_exit_reason(vcpu);
--
2.46.0.598.g6f2099f65c-goog