x86/resctrl: Add CPU online callback for resctrl work

The resctrl architecture specific code may need to create a domain when a CPU
comes online, it also needs to reset the CPUs PQR_ASSOC register.  The resctrl
filesystem code needs to update the rdtgroup_default CPU mask when CPUs are
brought online.

Currently, this is all done in one function, resctrl_online_cpu().  It will
need to be split into architecture and filesystem parts before resctrl can be
moved to /fs/.

Pull the rdtgroup_default update work out as a filesystem specific cpu_online
helper. resctrl_online_cpu() is the obvious name for this, which means the
version in core.c needs renaming.

resctrl_online_cpu() is called by the arch code once it has done the work to
add the new CPU to any domains.

In future patches, resctrl_online_cpu() will take the rdtgroup_mutex itself.

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/20240213184438.16675-21-james.morse@arm.com
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>

Author: James Morse

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

@@ -606,16 +606,16 @@ static void clear_closid_rmid(int cpu)
 	      RESCTRL_RESERVED_CLOSID);
 }
 
-static int resctrl_online_cpu(unsigned int cpu)
+static int resctrl_arch_online_cpu(unsigned int cpu)
 {
 	struct rdt_resource *r;
 
 	mutex_lock(&rdtgroup_mutex);
 	for_each_capable_rdt_resource(r)
 		domain_add_cpu(cpu, r);
-	/* The cpu is set in default rdtgroup after online. */
-	cpumask_set_cpu(cpu, &rdtgroup_default.cpu_mask);
 	clear_closid_rmid(cpu);
+
+	resctrl_online_cpu(cpu);
 	mutex_unlock(&rdtgroup_mutex);
 
 	return 0;
@@ -967,7 +967,7 @@ static int __init resctrl_late_init(void)
 
 	state = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
 				  "x86/resctrl/cat:online:",
-				  resctrl_online_cpu, resctrl_offline_cpu);
+				  resctrl_arch_online_cpu, resctrl_offline_cpu);
 	if (state < 0)
 		return state;
 

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

@@ -4007,6 +4007,14 @@ int resctrl_online_domain(struct rdt_resource *r, struct rdt_domain *d)
 	return 0;
 }
 
+void resctrl_online_cpu(unsigned int cpu)
+{
+	lockdep_assert_held(&rdtgroup_mutex);
+
+	/* The CPU is set in default rdtgroup after online. */
+	cpumask_set_cpu(cpu, &rdtgroup_default.cpu_mask);
+}
+
 /*
  * rdtgroup_init - rdtgroup initialization
  *

include/linux/resctrl.h

@@ -223,6 +223,7 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_domain *d,
 			    u32 closid, enum resctrl_conf_type type);
 int resctrl_online_domain(struct rdt_resource *r, struct rdt_domain *d);
 void resctrl_offline_domain(struct rdt_resource *r, struct rdt_domain *d);
+void resctrl_online_cpu(unsigned int cpu);
 
 /**
  * resctrl_arch_rmid_read() - Read the eventid counter corresponding to rmid