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| author | Xiaochen Shen <shenxiaochen@open-hieco.net> | 2025-12-17 06:04:53 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-02-27 02:00:39 +0300 |
| commit | acbb3cbbae55f6c7fb737fade3c3471182eecb30 (patch) | |
| tree | b18a3cc38c61afff8f8152c8fa7174e67ff368e0 /tools/testing | |
| parent | e889cf98412af0adcb367188a6b33f039a694bd4 (diff) | |
| download | linux-acbb3cbbae55f6c7fb737fade3c3471182eecb30.tar.xz | |
selftests/resctrl: Fix a division by zero error on Hygon
[ Upstream commit 671ef08d9455f5754d1fc96f5a14e357d6b80936 ]
Change to adjust effective L3 cache size with SNC enabled change
introduced the snc_nodes_per_l3_cache() function to detect the Intel
Sub-NUMA Clustering (SNC) feature by comparing #CPUs in node0 with #CPUs
sharing LLC with CPU0. The function was designed to return:
(1) >1: SNC mode is enabled.
(2) 1: SNC mode is not enabled or not supported.
However, on certain Hygon CPUs, #CPUs sharing LLC with CPU0 is actually
less than #CPUs in node0. This results in snc_nodes_per_l3_cache()
returning 0 (calculated as cache_cpus / node_cpus).
This leads to a division by zero error in get_cache_size():
*cache_size /= snc_nodes_per_l3_cache();
Causing the resctrl selftest to fail with:
"Floating point exception (core dumped)"
Fix the issue by ensuring snc_nodes_per_l3_cache() returns 1 when SNC
mode is not supported on the platform.
Updated commit log to fix commit has issues:
Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/20251217030456.3834956-2-shenxiaochen@open-hieco.net
Fixes: a1cd99e700ec ("selftests/resctrl: Adjust effective L3 cache size with SNC enabled")
Signed-off-by: Xiaochen Shen <shenxiaochen@open-hieco.net>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Fenghua Yu <fenghuay@nvidia.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'tools/testing')
| -rw-r--r-- | tools/testing/selftests/resctrl/resctrlfs.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/tools/testing/selftests/resctrl/resctrlfs.c b/tools/testing/selftests/resctrl/resctrlfs.c index 195f04c4d158..b9c1bfb6cc02 100644 --- a/tools/testing/selftests/resctrl/resctrlfs.c +++ b/tools/testing/selftests/resctrl/resctrlfs.c @@ -243,6 +243,16 @@ int snc_nodes_per_l3_cache(void) } snc_mode = cache_cpus / node_cpus; + /* + * On some platforms (e.g. Hygon), + * cache_cpus < node_cpus, the calculated snc_mode is 0. + * + * Set snc_mode = 1 to indicate that SNC mode is not + * supported on the platform. + */ + if (!snc_mode) + snc_mode = 1; + if (snc_mode > 1) ksft_print_msg("SNC-%d mode discovered.\n", snc_mode); } |