linux-kernel - Re: [PATCH v2 7/7] selftests/mm: Skip hugepage-mremap test if userfaultfd unavailable

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Message-ID: <d6ded113-2fab-45a1-94dc-5cde0c9f9006@redhat.com>
Date: Thu, 3 Jul 2025 10:38:50 +0200
From: David Hildenbrand <david@...hat.com>
To: Aboorva Devarajan <aboorvad@...ux.ibm.com>, akpm@...ux-foundation.org,
 Liam.Howlett@...cle.com, lorenzo.stoakes@...cle.com, shuah@...nel.org,
 pfalcato@...e.de, ziy@...dia.com, baolin.wang@...ux.alibaba.com,
 npache@...hat.com, ryan.roberts@....com, dev.jain@....com, baohua@...nel.org
Cc: linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org, donettom@...ux.ibm.com, ritesh.list@...il.com
Subject: Re: [PATCH v2 7/7] selftests/mm: Skip hugepage-mremap test if
 userfaultfd unavailable

On 03.07.25 08:06, Aboorva Devarajan wrote:
> Gracefully skip test if userfaultfd is not supported (ENOSYS) or not
> permitted (EPERM), instead of failing. This avoids misleading failures
> with clear skip messages.
> --------------
> Before Patch
> --------------
> ~ running ./hugepage-mremap
> ...
> ~ Bail out! userfaultfd: Function not implemented
> ~ Planned tests != run tests (1 != 0)
> ~ Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
> ~ [FAIL]
> not ok 4 hugepage-mremap # exit=1
> 
> --------------
> After Patch
> --------------
> ~ running ./hugepage-mremap
> ...
> ~ ok 2 # SKIP userfaultfd is not supported/not enabled.
> ~ 1 skipped test(s) detected.
> ~ Totals: pass:0 fail:0 xfail:0 xpass:0 skip:1 error:0
> ~ [SKIP]
> ok 4 hugepage-mremap # SKIP
> 
> Signed-off-by: Aboorva Devarajan <aboorvad@...ux.ibm.com>
> ---
>   tools/testing/selftests/mm/hugepage-mremap.c | 16 +++++++++++++---
>   1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/hugepage-mremap.c b/tools/testing/selftests/mm/hugepage-mremap.c
> index c463d1c09c9b..1a0e6dd87578 100644
> --- a/tools/testing/selftests/mm/hugepage-mremap.c
> +++ b/tools/testing/selftests/mm/hugepage-mremap.c
> @@ -65,10 +65,20 @@ static void register_region_with_uffd(char *addr, size_t len)
>   	struct uffdio_api uffdio_api;
>   
>   	/* Create and enable userfaultfd object. */
> -
>   	uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
> -	if (uffd == -1)
> -		ksft_exit_fail_msg("userfaultfd: %s\n", strerror(errno));
> +	if (uffd == -1) {
> +		switch (errno) {
> +		case EPERM:
> +			ksft_exit_skip("No userfaultfd permissions, try running as root.\n");

"Insufficient permissions, try ..." ?

> +			break;
> +		case ENOSYS:
> +			ksft_exit_skip("userfaultfd is not supported/not enabled.\n");
> +			break;

Note that we have in tools/testing/selftests/mm/config

	CONFIG_USERFAULTFD=y

But I don't have anything about making the test more versatile.

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb