From cc2ca4296f72519686a9f949e725275f497f90ae Mon Sep 17 00:00:00 2001 From: Reinette Chatre Date: Tue, 30 Jun 2026 21:27:05 -0700 Subject: [PATCH] fs/resctrl: Pass error reading event through to user space Reading of event data is managed through populating a struct rmid_read with properties of event needing to be read. This data is dispatched to an appropriate CPU and upon completion any error can be found in rmid_read::err, or on success the event data will be in rmid_read::val. rmid_read::err is not updated in the unlikely scenario that the reading of the event was dispatched to a wrong CPU. If this ever occurs due to a bug in resctrl the user space read will return "success" but the data reported will be invalid. Ensure accurate error reporting so that if there may be an issue with how resctrl picks a CPU it could be learned with an error to user space instead of silent failure. Signed-off-by: Reinette Chatre Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Ben Horgan Reviewed-by: Tony Luck Tested-by: Babu Moger Link: https://patch.msgid.link/6b3c66a49788828bd8c04a6911bd74c91ccd56f3.1782857711.git.reinette.chatre@intel.com --- fs/resctrl/monitor.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c index 29b13a690cf3..7f3fe055f7c9 100644 --- a/fs/resctrl/monitor.c +++ b/fs/resctrl/monitor.c @@ -458,8 +458,10 @@ static int __l3_mon_event_count(struct rdtgroup *rdtgrp, struct rmid_read *rr) } /* Reading a single domain, must be on a CPU in that domain. */ - if (!cpumask_test_cpu(cpu, &d->hdr.cpu_mask)) + if (!cpumask_test_cpu(cpu, &d->hdr.cpu_mask)) { + rr->err = -EIO; return -EINVAL; + } if (rr->is_mbm_cntr) rr->err = resctrl_arch_cntr_read(rr->r, d, closid, rmid, cntr_id, rr->evt->evtid, &tval); @@ -496,8 +498,10 @@ static int __l3_mon_event_count_sum(struct rdtgroup *rdtgrp, struct rmid_read *r } /* Summing domains that share a cache, must be on a CPU for that cache. */ - if (!cpumask_test_cpu(cpu, &rr->ci->shared_cpu_map)) + if (!cpumask_test_cpu(cpu, &rr->ci->shared_cpu_map)) { + rr->err = -EIO; return -EINVAL; + } /* * Legacy files must report the sum of an event across all