Commit
a1cd99e700ec ("selftests/resctrl: Adjust effective L3 cache size with SNC enabled")
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.
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 --- tools/testing/selftests/resctrl/resctrlfs.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
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); }