linux-kernel - Re: [PATCH 3/3] userfaultfd: selftest: Report XFAIL if shmem doesn't support zeropage

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Message-Id: <20180725141849.GE25188@rapoport-lnx>
Date:   Wed, 25 Jul 2018 17:18:49 +0300
From:   Mike Rapoport <rppt@...ux.vnet.ibm.com>
To:     Thiago Jung Bauermann <bauerman@...ux.ibm.com>
Cc:     linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        Shuah Khan <shuah@...nel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Prakash Sangappa <prakash.sangappa@...cle.com>
Subject: Re: [PATCH 3/3] userfaultfd: selftest: Report XFAIL if shmem doesn't
 support zeropage

Hi,

On Tue, Jul 24, 2018 at 11:42:09PM -0300, Thiago Jung Bauermann wrote:
> If userfaultfd runs on a system that doesn't support UFFDIO_ZEROPAGE for
> shared memory, it currently ends with error code 1 which indicates test
> failure:
> 
>   # ./userfaultfd shmem 10 10
>   nr_pages: 160, nr_pages_per_cpu: 80
>   bounces: 9, mode: rnd poll, unexpected missing ioctl for anon memory
>   # echo $?
>   1
> 
> This is a real failure, but expected so signal that to the test harness:

I don't think its a real failure. If the kernel does not support
UFFDIO_ZEROPAGE for shared memory the userfaultfd_zeropage_test can be
simply skipped.
 
>   # ./userfaultfd shmem 10 10
>   nr_pages: 160, nr_pages_per_cpu: 80
>   bounces: 9, mode: rnd poll, UFFDIO_ZEROPAGE unsupported in shmem VMAs
>   # echo $?
>   2
> 
> Signed-off-by: Thiago Jung Bauermann <bauerman@...ux.ibm.com>
> ---
>  tools/testing/selftests/vm/userfaultfd.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
> index bc9ec38fbc34..686fe96f617f 100644
> --- a/tools/testing/selftests/vm/userfaultfd.c
> +++ b/tools/testing/selftests/vm/userfaultfd.c
> @@ -1115,6 +1115,14 @@ static int userfaultfd_stress(void)
>  		expected_ioctls = uffd_test_ops->expected_ioctls;
>  		if ((uffdio_register.ioctls & expected_ioctls) !=
>  		    expected_ioctls) {
> +			if (test_type == TEST_SHMEM &&
> +			    (uffdio_register.ioctls & expected_ioctls) ==
> +			    UFFD_API_RANGE_IOCTLS_BASIC) {
> +				fprintf(stderr,
> +					"UFFDIO_ZEROPAGE unsupported in shmem VMAs\n");
> +				return KSFT_XFAIL;
> +			}
> +

By all means, this check should be moved to userfaultfd_zeropage_test().
Ideally, we should call here ksft_test_result_skip() and simply return from
the function.



>  			fprintf(stderr,
>  				"unexpected missing ioctl for anon memory\n");
>  			return 1;

-- 
Sincerely yours,
Mike.