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

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Message-ID: <4D78BC13-74C9-4570-A81B-B7094B16A336@nvidia.com>
Date: Thu, 03 Jul 2025 10:52:31 -0400
From: Zi Yan <ziy@...dia.com>
To: David Hildenbrand <david@...hat.com>
Cc: Aboorva Devarajan <aboorvad@...ux.ibm.com>, akpm@...ux-foundation.org,
 Liam.Howlett@...cle.com, lorenzo.stoakes@...cle.com, shuah@...nel.org,
 pfalcato@...e.de, baolin.wang@...ux.alibaba.com, npache@...hat.com,
 ryan.roberts@....com, dev.jain@....com, baohua@...nel.org,
 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 3 Jul 2025, at 4:38, David Hildenbrand wrote:

> 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

I added the same fix to guard-regions.c since I did not know the config
file existed.

And from git history, I learnt that I could use the command below to merge
these config to my local config:
“./scripts/kconfig/merge_config.sh .config tools/testing/selftests/xxx/config”

Reviewed-by: Zi Yan <ziy@...dia.com>

Best Regards,
Yan, Zi