x86/resctrl: Move domain helper migration into resctrl_offline_cpu()

When a CPU is taken offline the resctrl filesystem code needs to check if it
was the CPU nominated to perform the periodic overflow and limbo work. If so,
another CPU needs to be chosen to do this work.

This is currently done in core.c, mixed in with the code that removes the CPU
from the domain's mask, and potentially free()s the domain.

Move the migration of the overflow and limbo helpers into the filesystem code,
into resctrl_offline_cpu(). As resctrl_offline_cpu() runs before the
architecture code has removed the CPU from the domain mask, the callers need to
be told which CPU is being removed, to avoid picking it as the new CPU. This
uses the exclude_cpu feature previously added.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Peter Newman <peternewman@google.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Tested-by: Carl Worth <carl@os.amperecomputing.com> # arm64
Link: https://lore.kernel.org/r/20240213184438.16675-24-james.morse@arm.com
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>

Author: James Morse

arch/x86/kernel/cpu/resctrl/core.c

@@ -580,22 +580,6 @@ static void domain_remove_cpu(int cpu, struct rdt_resource *r)
 
 		return;
 	}
-
-	if (r == &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl) {
-		if (is_mbm_enabled() && cpu == d->mbm_work_cpu) {
-			cancel_delayed_work(&d->mbm_over);
-			/*
-			 * temporary: exclude_cpu=-1 as this CPU has already
-			 * been removed by cpumask_clear_cpu()d
-			 */
-			mbm_setup_overflow_handler(d, 0, RESCTRL_PICK_ANY_CPU);
-		}
-		if (is_llc_occupancy_enabled() && cpu == d->cqm_work_cpu &&
-		    has_busy_rmid(d)) {
-			cancel_delayed_work(&d->cqm_limbo);
-			cqm_setup_limbo_handler(d, 0, RESCTRL_PICK_ANY_CPU);
-		}
-	}
 }
 
 static void clear_closid_rmid(int cpu)

arch/x86/kernel/cpu/resctrl/rdtgroup.c

@@ -4029,7 +4029,9 @@ static void clear_childcpus(struct rdtgroup *r, unsigned int cpu)
 
 void resctrl_offline_cpu(unsigned int cpu)
 {
+	struct rdt_resource *l3 = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
 	struct rdtgroup *rdtgrp;
+	struct rdt_domain *d;
 
 	lockdep_assert_held(&rdtgroup_mutex);
 
@@ -4039,6 +4041,22 @@ void resctrl_offline_cpu(unsigned int cpu)
 			break;
 		}
 	}
+
+	if (!l3->mon_capable)
+		return;
+
+	d = get_domain_from_cpu(cpu, l3);
+	if (d) {
+		if (is_mbm_enabled() && cpu == d->mbm_work_cpu) {
+			cancel_delayed_work(&d->mbm_over);
+			mbm_setup_overflow_handler(d, 0, cpu);
+		}
+		if (is_llc_occupancy_enabled() && cpu == d->cqm_work_cpu &&
+		    has_busy_rmid(d)) {
+			cancel_delayed_work(&d->cqm_limbo);
+			cqm_setup_limbo_handler(d, 0, cpu);
+		}
+	}
 }
 
 /*