Commit 6f49693a authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'smp-core-2023-08-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull CPU hotplug updates from Thomas Gleixner:
 "Updates for the CPU hotplug core:

   - Support partial SMT enablement.

     So far the sysfs SMT control only allows to toggle between SMT on
     and off. That's sufficient for x86 which usually has at max two
     threads except for the Xeon PHI platform which has four threads per
     core

     Though PowerPC has up to 16 threads per core and so far it's only
     possible to control the number of enabled threads per core via a
     command line option. There is some way to control this at runtime,
     but that lacks enforcement and the usability is awkward

     This update expands the sysfs interface and the core infrastructure
     to accept numerical values so PowerPC can build SMT runtime control
     for partial SMT enablement on top

     The core support has also been provided to the PowerPC maintainers
     who added the PowerPC related changes on top

   - Minor cleanups and documentation updates"

* tag 'smp-core-2023-08-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Documentation: core-api/cpuhotplug: Fix state names
  cpu/hotplug: Remove unused function declaration cpu_set_state_online()
  cpu/SMT: Fix cpu_smt_possible() comment
  cpu/SMT: Allow enabling partial SMT states via sysfs
  cpu/SMT: Create topology_smt_thread_allowed()
  cpu/SMT: Remove topology_smt_supported()
  cpu/SMT: Store the current/max number of threads
  cpu/SMT: Move smt/control simple exit cases earlier
  cpu/SMT: Move SMT prototypes into cpu_smt.h
  cpu/hotplug: Remove dependancy against cpu_primary_thread_mask
parents dd3f0fe5 e0a99a83

Documentation/ABI/testing/sysfs-devices-system-cpu

+1 −0
Original line number Diff line number Diff line
@@ -556,6 +556,7 @@ Description: Control Symmetric Multi Threading (SMT) 
			 ================ =========================================

			 "on"		  SMT is enabled

			 "off"		  SMT is disabled

			 "<N>"		  SMT is enabled with N threads per core.

			 "forceoff"	  SMT is force disabled. Cannot be changed.

			 "notsupported"   SMT is not supported by the CPU

			 "notimplemented" SMT runtime toggling is not

Documentation/core-api/cpu_hotplug.rst

+5 −5
Original line number Diff line number Diff line
@@ -395,8 +395,8 @@ multi-instance state the following function is available: 
* cpuhp_setup_state_multi(state, name, startup, teardown)



The @state argument is either a statically allocated state or one of the

constants for dynamically allocated states - CPUHP_PREPARE_DYN,

CPUHP_ONLINE_DYN - depending on the state section (PREPARE, ONLINE) for

constants for dynamically allocated states - CPUHP_BP_PREPARE_DYN,

CPUHP_AP_ONLINE_DYN - depending on the state section (PREPARE, ONLINE) for

which a dynamic state should be allocated.



The @name argument is used for sysfs output and for instrumentation. The
@@ -588,7 +588,7 @@ notifications on online and offline operations:: 
Setup and teardown a dynamically allocated state in the ONLINE section

for notifications on offline operations::



   state = cpuhp_setup_state(CPUHP_ONLINE_DYN, "subsys:offline", NULL, subsys_cpu_offline);

   state = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "subsys:offline", NULL, subsys_cpu_offline);

   if (state < 0)

       return state;

   ....
@@ -597,7 +597,7 @@ for notifications on offline operations:: 
Setup and teardown a dynamically allocated state in the ONLINE section

for notifications on online operations without invoking the callbacks::



   state = cpuhp_setup_state_nocalls(CPUHP_ONLINE_DYN, "subsys:online", subsys_cpu_online, NULL);

   state = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "subsys:online", subsys_cpu_online, NULL);

   if (state < 0)

       return state;

   ....
@@ -606,7 +606,7 @@ for notifications on online operations without invoking the callbacks:: 
Setup, use and teardown a dynamically allocated multi-instance state in the

ONLINE section for notifications on online and offline operation::



   state = cpuhp_setup_state_multi(CPUHP_ONLINE_DYN, "subsys:online", subsys_cpu_online, subsys_cpu_offline);

   state = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "subsys:online", subsys_cpu_online, subsys_cpu_offline);

   if (state < 0)

       return state;

   ....

arch/Kconfig

+3 −0
Original line number Diff line number Diff line
@@ -34,6 +34,9 @@ config ARCH_HAS_SUBPAGE_FAULTS 
config HOTPLUG_SMT

	bool



config SMT_NUM_THREADS_DYNAMIC

	bool



# Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL

config HOTPLUG_CORE_SYNC

	bool

arch/x86/include/asm/topology.h

+2 −2
Original line number Diff line number Diff line
@@ -136,10 +136,11 @@ static inline int topology_max_smt_threads(void) 
	return __max_smt_threads;

}



#include <linux/cpu_smt.h>



int topology_update_package_map(unsigned int apicid, unsigned int cpu);

int topology_update_die_map(unsigned int dieid, unsigned int cpu);

int topology_phys_to_logical_pkg(unsigned int pkg);

bool topology_smt_supported(void);



extern struct cpumask __cpu_primary_thread_mask;

#define cpu_primary_thread_mask ((const struct cpumask *)&__cpu_primary_thread_mask)
@@ -162,7 +163,6 @@ static inline int topology_phys_to_logical_pkg(unsigned int pkg) { return 0; } 
static inline int topology_max_die_per_package(void) { return 1; }

static inline int topology_max_smt_threads(void) { return 1; }

static inline bool topology_is_primary_thread(unsigned int cpu) { return true; }

static inline bool topology_smt_supported(void) { return false; }

#endif /* !CONFIG_SMP */



static inline void arch_fix_phys_package_id(int num, u32 slot)

arch/x86/kernel/cpu/common.c

+1 −1
Original line number Diff line number Diff line
@@ -2343,7 +2343,7 @@ void __init arch_cpu_finalize_init(void) 
	 * identify_boot_cpu() initialized SMT support information, let the

	 * core code know.

	 */

	cpu_smt_check_topology();

	cpu_smt_set_num_threads(smp_num_siblings, smp_num_siblings);



	if (!IS_ENABLED(CONFIG_SMP)) {

		pr_info("CPU: ");