guest_memfd_test.c uses MADV_COLLAPSE unconditionally, but the constant was only exposed in glibc 2.37. Distros still on older glibc (e.g. Debian Bookworm, glibc 2.36) cannot build the test. Add a compile-time fallback that defines MADV_COLLAPSE to its kernel-ABI value when the libc header does not, matching the established selftest pattern for sometimes-missing libc constants (see selftests/bpf/uprobe_multi.c, selftests/mm/hugetlb-soft-offline.c). Fixes: 9830209b4ae8 ("KVM: selftests: Test MADV_COLLAPSE on guest_memfd") Signed-off-by: Fuad Tabba --- tools/testing/selftests/kvm/guest_memfd_test.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c index d6528c6f5e03..45990ae5f1e5 100644 --- a/tools/testing/selftests/kvm/guest_memfd_test.c +++ b/tools/testing/selftests/kvm/guest_memfd_test.c @@ -23,6 +23,10 @@ #include "test_util.h" #include "ucall_common.h" +#ifndef MADV_COLLAPSE +#define MADV_COLLAPSE 25 +#endif + static size_t page_size; static void test_file_read_write(int fd, size_t total_size) -- 2.54.0.563.g4f69b47b94-goog