Re: [PATCH v2 2/2] selftests/x86/amx: Test dynamic fpstate cleanup across exec()

["Chang S. Bae" <chang.seok.bae@intel.com>]

On 10/7/2026 10:59 PM, Guixiong Wei wrote:
>   
> -int main(void)
> +static int count_dynamic_fpstates(void)
> +{
> +	char *line = NULL;
> +	size_t line_size = 0;
> +	FILE *fp;
> +	int count = 0;
> +
> +	fp = fopen("/proc/vmallocinfo", "r");
> +	if (!fp)
> +		return -errno;

The call site doesn't interprete the error code. Instead, you can simply 
call fatal_error() here and below on an IO error.

> +
> +	while (getline(&line, &line_size, fp) >= 0) {
> +		if (strstr(line, "__xfd_enable_feature") ||
> +		    strstr(line, "fpstate_realloc"))
> +			count++;
> +	}
> +
> +	if (ferror(fp))
> +		count = -EIO;
> +
> +	free(line);
> +	fclose(fp);
> +	return count;
> +}

> +static void test_exec(void)
> +{
> +	char iterations_arg[16];
> +	char baseline_arg[16];
> +	int before, after, delta;
> +	pid_t child;
> +	int status;
> +
> +	printf("[RUN]\tCheck dynamic fpstate cleanup across exec().\n");
> +
> +	before = count_dynamic_fpstates();
> +	if (before < 0) {
> +		printf("[SKIP]\tCannot read /proc/vmallocinfo: %s\n",
> +		       strerror(-before));
> +		return;
> +	}
> +
> +	child = fork();
> +	if (child < 0)
> +		fatal_error("fork");
> +	if (!child) {
> +		snprintf(iterations_arg, sizeof(iterations_arg), "%d",
> +			 EXEC_TEST_ITERS);
> +		snprintf(baseline_arg, sizeof(baseline_arg), "%d", before);
> +		execl("/proc/self/exe", "amx", EXEC_TEST_ARG, iterations_arg,
> +		      baseline_arg, NULL);
> +		fatal_error("exec");
> +	}

This nested exec() with passing numbers via arguments looks more 
complicate than necessary.

Instead, you could put the fork()/exec() sequence in a loop. Before each 
exec(), call load_rand_tiledata(), and adjust main() to return 
immediately from the exec test. I found this also reproduces the 
increase in /proc/vmallocinfo.

> +
> +	if (waitpid(child, &status, 0) != child)
> +		fatal_error("waitpid");
> +	if (WIFEXITED(status) && WEXITSTATUS(status) == KSFT_SKIP) {
> +		printf("[SKIP]\tDynamic fpstate allocation was not isolated.\n");
> +		return;
> +	}
> +	if (!WIFEXITED(status) || WEXITSTATUS(status))
> +		fatal_error("exec test child");
> +
> +	after = count_dynamic_fpstates();
> +	if (after < 0) {
> +		printf("[SKIP]\tCannot read /proc/vmallocinfo after exec(): %s\n",
> +		       strerror(-after));
> +		return;
> +	}
> +
> +	delta = after - before;
> +	if (!delta) {
> +		printf("[OK]\tDynamic fpstate allocations were freed across exec().\n");
> +		return;
> +	}
> +
> +	if (delta == EXEC_TEST_ITERS)
> +		errx(1, "[FAIL]\texec() leaked %d dynamic fpstate allocations",
> +		     delta);

errx() terminates the entire test, preventing subsequent tests from 
running. Unless this failure makes it unsafe or meaningless to continue, 
why not report the failure with printf() and let the remaining tests run?

> +
> +	printf("[SKIP]\tDynamic fpstate vmalloc usage changed concurrently.\n");
> +}

Thanks,
Chang