x86/resctrl: Refactor domain_remove_cpu_mon() ready for new domain types

New telemetry events will be associated with a new package scoped resource
with a new domain structure.

Refactor domain_remove_cpu_mon() so all the L3 domain processing is separate
from the general domain action of clearing the CPU bit in the mask.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/20251217172121.12030-1-tony.luck@intel.com

Author: aegl

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

@@ -631,9 +631,7 @@ static void domain_remove_cpu_ctrl(int cpu, struct rdt_resource *r)
 static void domain_remove_cpu_mon(int cpu, struct rdt_resource *r)
 {
 	int id = get_domain_id_from_scope(cpu, r->mon_scope);
-	struct rdt_hw_mon_domain *hw_dom;
 	struct rdt_domain_hdr *hdr;
-	struct rdt_mon_domain *d;
 
 	lockdep_assert_held(&domain_list_lock);
 
@@ -650,20 +648,29 @@ static void domain_remove_cpu_mon(int cpu, struct rdt_resource *r)
 		return;
 	}
 
-	if (!domain_header_is_valid(hdr, RESCTRL_MON_DOMAIN, r->rid))
+	cpumask_clear_cpu(cpu, &hdr->cpu_mask);
+	if (!cpumask_empty(&hdr->cpu_mask))
 		return;
 
-	d = container_of(hdr, struct rdt_mon_domain, hdr);
-	hw_dom = resctrl_to_arch_mon_dom(d);
+	switch (r->rid) {
+	case RDT_RESOURCE_L3: {
+		struct rdt_hw_mon_domain *hw_dom;
+		struct rdt_mon_domain *d;
 
-	cpumask_clear_cpu(cpu, &d->hdr.cpu_mask);
-	if (cpumask_empty(&d->hdr.cpu_mask)) {
+		if (!domain_header_is_valid(hdr, RESCTRL_MON_DOMAIN, RDT_RESOURCE_L3))
+			return;
+
+		d = container_of(hdr, struct rdt_mon_domain, hdr);
+		hw_dom = resctrl_to_arch_mon_dom(d);
 		resctrl_offline_mon_domain(r, d);
-		list_del_rcu(&d->hdr.list);
+		list_del_rcu(&hdr->list);
 		synchronize_rcu();
 		mon_domain_free(hw_dom);
-
-		return;
+		break;
+	}
+	default:
+		pr_warn_once("Unknown resource rid=%d\n", r->rid);
+		break;
 	}
 }