From db64994d115e7c2cd72fec11b854467e97169379 Mon Sep 17 00:00:00 2001 From: Tony Luck Date: Wed, 17 Dec 2025 09:21:02 -0800 Subject: [PATCH] fs/resctrl: Emphasize that L3 monitoring resource is required for summing domains The feature to sum event data across multiple domains supports systems with Sub-NUMA Cluster (SNC) mode enabled. The top-level monitoring files in each "mon_L3_XX" directory provide the sum of data across all SNC nodes sharing an L3 cache instance while the "mon_sub_L3_YY" sub-directories provide the event data of the individual nodes. SNC is only associated with the L3 resource and domains and as a result the flow handling the sum of event data implicitly assumes it is working with the L3 resource and domains. Reading of telemetry events does not require to sum event data so this feature can remain dedicated to SNC and keep the implicit assumption of working with the L3 resource and domains. Add a WARN to where the implicit assumption of working with the L3 resource is made and add comments on how the structure controlling the event sum feature is used. Suggested-by: Reinette Chatre Signed-off-by: Tony Luck Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Reinette Chatre Link: https://lore.kernel.org/20251217172121.12030-1-tony.luck@intel.com --- fs/resctrl/ctrlmondata.c | 8 +++++++- fs/resctrl/internal.h | 4 ++-- fs/resctrl/rdtgroup.c | 3 ++- 3 files changed, 11 insertions(+), 4 deletions(-) diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c index f319fd1a6de31..cc4237c57cbe4 100644 --- a/fs/resctrl/ctrlmondata.c +++ b/fs/resctrl/ctrlmondata.c @@ -677,7 +677,6 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg) { struct kernfs_open_file *of = m->private; enum resctrl_res_level resid; - struct rdt_l3_mon_domain *d; struct rdt_domain_hdr *hdr; struct rmid_read rr = {0}; struct rdtgroup *rdtgrp; @@ -705,6 +704,13 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg) r = resctrl_arch_get_resource(resid); if (md->sum) { + struct rdt_l3_mon_domain *d; + + if (WARN_ON_ONCE(resid != RDT_RESOURCE_L3)) { + ret = -EINVAL; + goto out; + } + /* * This file requires summing across all domains that share * the L3 cache id that was provided in the "domid" field of the diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h index 0110d1175398c..50d88e91e0daa 100644 --- a/fs/resctrl/internal.h +++ b/fs/resctrl/internal.h @@ -92,8 +92,8 @@ extern struct mon_evt mon_event_all[QOS_NUM_EVENTS]; * @list: Member of the global @mon_data_kn_priv_list list. * @rid: Resource id associated with the event file. * @evt: Event structure associated with the event file. - * @sum: Set when event must be summed across multiple - * domains. + * @sum: Set for RDT_RESOURCE_L3 when event must be summed + * across multiple domains. * @domid: When @sum is zero this is the domain to which * the event file belongs. When @sum is one this * is the id of the L3 cache that all domains to be diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c index a06cefd2a09e8..a2ad99acedd66 100644 --- a/fs/resctrl/rdtgroup.c +++ b/fs/resctrl/rdtgroup.c @@ -3096,7 +3096,8 @@ static void rmdir_all_sub(void) * @rid: The resource id for the event file being created. * @domid: The domain id for the event file being created. * @mevt: The type of event file being created. - * @do_sum: Whether SNC summing monitors are being created. + * @do_sum: Whether SNC summing monitors are being created. Only set + * when @rid == RDT_RESOURCE_L3. */ static struct mon_data *mon_get_kn_priv(enum resctrl_res_level rid, int domid, struct mon_evt *mevt, -- 2.47.3