Patch "selftests/resctrl: Print accurate buffer size as part of MBM results" has been added to the 6.11-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    selftests/resctrl: Print accurate buffer size as part of MBM results

to the 6.11-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     selftests-resctrl-print-accurate-buffer-size-as-part.patch
and it can be found in the queue-6.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 6c5f32b6984f469331c6b27d4b3edc8b051fa435
Author: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Date:   Thu Oct 24 14:18:39 2024 -0700

    selftests/resctrl: Print accurate buffer size as part of MBM results
    
    [ Upstream commit 1b4840395f08e9723a15fea42c2d31090e8375f3 ]
    
    By default the MBM test uses the "fill_buf" benchmark to keep reading
    from a buffer with size DEFAULT_SPAN while measuring memory bandwidth.
    User space can provide an alternate benchmark or amend the size of
    the buffer "fill_buf" should use.
    
    Analysis of the MBM measurements do not require that a buffer be used
    and thus do not require knowing the size of the buffer if it was used
    during testing. Even so, the buffer size is printed as informational
    as part of the MBM test results. What is printed as buffer size is
    hardcoded as DEFAULT_SPAN, even if the test relied on another benchmark
    (that may or may not use a buffer) or if user space amended the buffer
    size.
    
    Ensure that accurate buffer size is printed when using "fill_buf"
    benchmark and omit the buffer size information if another benchmark
    is used.
    
    Fixes: ecdbb911f22d ("selftests/resctrl: Add MBM test")
    Signed-off-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
    Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
    Signed-off-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/tools/testing/selftests/resctrl/mbm_test.c b/tools/testing/selftests/resctrl/mbm_test.c
index 6b5a3b52d861b..cf08ba5e314e2 100644
--- a/tools/testing/selftests/resctrl/mbm_test.c
+++ b/tools/testing/selftests/resctrl/mbm_test.c
@@ -40,7 +40,8 @@ show_bw_info(unsigned long *bw_imc, unsigned long *bw_resc, size_t span)
 	ksft_print_msg("%s Check MBM diff within %d%%\n",
 		       ret ? "Fail:" : "Pass:", MAX_DIFF_PERCENT);
 	ksft_print_msg("avg_diff_per: %d%%\n", avg_diff_per);
-	ksft_print_msg("Span (MB): %zu\n", span / MB);
+	if (span)
+		ksft_print_msg("Span (MB): %zu\n", span / MB);
 	ksft_print_msg("avg_bw_imc: %lu\n", avg_bw_imc);
 	ksft_print_msg("avg_bw_resc: %lu\n", avg_bw_resc);
 
@@ -138,15 +139,26 @@ static int mbm_run_test(const struct resctrl_test *test, const struct user_param
 		.setup		= mbm_setup,
 		.measure	= mbm_measure,
 	};
+	char *endptr = NULL;
+	size_t span = 0;
 	int ret;
 
 	remove(RESULT_FILE_NAME);
 
+	if (uparams->benchmark_cmd[0] && strcmp(uparams->benchmark_cmd[0], "fill_buf") == 0) {
+		if (uparams->benchmark_cmd[1] && *uparams->benchmark_cmd[1] != '\0') {
+			errno = 0;
+			span = strtoul(uparams->benchmark_cmd[1], &endptr, 10);
+			if (errno || *endptr != '\0')
+				return -EINVAL;
+		}
+	}
+
 	ret = resctrl_val(test, uparams, uparams->benchmark_cmd, &param);
 	if (ret)
 		return ret;
 
-	ret = check_results(DEFAULT_SPAN);
+	ret = check_results(span);
 	if (ret && (get_vendor() == ARCH_INTEL))
 		ksft_print_msg("Intel MBM may be inaccurate when Sub-NUMA Clustering is enabled. Check BIOS configuration.\n");