Re: [PATCH] selftests/mm: ksm_tests: skip when not run as root

[Andrew Morton]

On Fri,  9 Jan 2026 17:43:13 +0800 Sun Jian <sun.jian.kdev@xxxxxxxxx> wrote:

> ksm_tests writes KSM sysfs knobs under /sys/kernel/mm/ksm, which requires
> root privileges. When run unprivileged, it fails with permission errors
> and reports FAIL, which is misleading.
> 
> Skip the test early when not run as root to avoid false failures.

Thanks.

When reissuing a patch it's nice to cc those individuals who commented
on previous versions.

> --- a/tools/testing/selftests/mm/ksm_tests.c
> +++ b/tools/testing/selftests/mm/ksm_tests.c
> @@ -766,6 +766,11 @@ int main(int argc, char *argv[])
>  	bool merge_across_nodes = KSM_MERGE_ACROSS_NODES_DEFAULT;
>  	long size_MB = 0;
>  
> +	if (geteuid() != 0) {
> +		printf("# SKIP ksm_tests requires root privileges\n");
> +		return KSFT_SKIP;
> +	}
> +

lgtm.  selftests/ code performs this test in about 20 places already,
all different.  In the interests of consistency and code cleanliness,
perhaps some kind person will centralize this check in some fashion!