reproduce:
        # https://github.com/agraf/linux-2.6/commit/ea39f95803e6da8a46791922be3724b49bea2c7a
        git remote add agraf-2.6 https://github.com/agraf/linux-2.6.git
        git fetch --no-tags agraf-2.6 kvm-kho-gmem-test
        git checkout ea39f95803e6da8a46791922be3724b49bea2c7a
        make W=1 O=/tmp/kselftest headers
        make W=1 O=/tmp/kselftest -C tools/testing/selftests
        make W=1 O=/tmp/kselftest -C tools/testing/selftests/bpf