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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 > Reviewed-by: Reinette Chatre > --- > 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..2b075e7334bf 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 certain Hygon platforms: nit. This situation could happen on other platforms than Hygon. Maybe it's better to have a more generic comment here? * On some platforms (e.g. Hygon), Reviewed-by: Fenghua Yu > + * 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); > } Thanks. -Fenghua