linux-kernel - Re: [PATCH] selftests:arm64: Test PR_SVE_VL

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Message-ID: <20240430122032.GA13690@willie-the-truck>
Date: Tue, 30 Apr 2024 13:20:32 +0100
From: Will Deacon <will@...nel.org>
To: Dorine Tipo <dorine.a.tipo@...il.com>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Shuah Khan <shuah@...nel.org>, linux-arm-kernel@...ts.infradead.org,
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-kernel-mentees@...ts.linuxfoundation.org,
	Javier Carrasco <javier.carrasco.cruz@...il.com>
Subject: Re: [PATCH] selftests:arm64: Test PR_SVE_VL_INHERIT after a double
 fork

On Mon, Apr 29, 2024 at 04:40:12AM +0000, Dorine Tipo wrote:
> Add a new test, double_fork_test() to check the inheritance of the SVE
> vector length after a double fork.
> The `EXPECTED_TESTS` macro has been updated to account for this additional
> test.
> This patch addresses task 7 on the TODO list.
> 
> Signed-off-by: Dorine Tipo <dorine.a.tipo@...il.com>
> ---
>  tools/testing/selftests/arm64/fp/za-fork.c | 95 +++++++++++++++++++++-
>  1 file changed, 94 insertions(+), 1 deletion(-)

I haven't tried compiling this, but some of the code looks a little off:

> diff --git a/tools/testing/selftests/arm64/fp/za-fork.c b/tools/testing/selftests/arm64/fp/za-fork.c
> index 587b94648222..35229e570dcf 100644
> --- a/tools/testing/selftests/arm64/fp/za-fork.c
> +++ b/tools/testing/selftests/arm64/fp/za-fork.c
> @@ -11,7 +11,7 @@
> 
>  #include "kselftest.h"
> 
> -#define EXPECTED_TESTS 1
> +#define EXPECTED_TESTS 2
> 
>  int fork_test(void);
>  int verify_fork(void);
> @@ -69,6 +69,97 @@ int fork_test_c(void)
> 	}
>  }
> 
> +int double_fork_test(void)
> +{
> +	pid_t newpid, grandchild_pid, waiting;
> +	int ret, child_status, parent_result;
> +
> +	ret = prctl(PR_SVE_SET_VL, vl | PR_SVE_VL_INHERIT);
> +	if (ret < 0)
> +		ksft_exit_fail_msg("Failed to set SVE VL %d\n", vl);
> +
> +	newpid = fork();
> +	if (newpid == 0) {
> +		/* In child */
> +		if (!verify_fork()) {
> +			ksft_print_msg("ZA state invalid in child\n");
> +			exit(0);
> +		}
> +
> +		grandchild_pid = fork();
> +		if (grandchild_pid == 0) {
> +			/* in grandchild */
> +			if (!verfy_fork()) {
> +				ksft_print_msg("ZA state invalid in grandchild\n");
> +				exit(0);
> +			}
> +
> +			ret = prctl(PR_SVE_GET_VL);
> +			if (ret & PR_SVE_VL_INHERIT) {
> +				ksft_print_msg("prctl() reports _INHERIT\n");
> +				return;

Missing return value?

> +			}
> +			 ksft_print_msg("prctl() does not report _INHERIT\n");

Indentation.

> +
> +		} else if (grandchild_pid < 0) {
> +			ksft_print_msg("fork() failed in first child: %d\n", grandchild_pid);
> +			return 0;
> +		}
> +
> +		/*  Wait for the grandchild process to exit */
> +		waiting = waitpid(grandchild_pid, &child_status, 0);
> +		if (waiting < 0) {
> +			if (errno == EINTR)
> +				continue;

'continue' outside of a loop?

> +			ksft_print_msg("waitpid() failed: %d\n", errno);
> +			return 0;
> +		}
> +		if (waiting != grandchild_pid) {
> +			ksft_print_msg("waitpid() returned wrong PID\n");
> +			return 0;
> +		}
> +
> +		if (!WIFEXITED(child_status)) {
> +			ksft_print_msg("grandchild did not exit\n");
> +			return 0;
> +		}
> +
> +		exit(1);
> +		}

Stray '}' ?

Will