Commit 8b5a0f95 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Peter Zijlstra
Browse files

x86/smpboot: Enable split CPU startup 



The x86 CPU bringup state currently does AP wake-up, wait for AP to
respond and then release it for full bringup.

It is safe to be split into a wake-up and and a separate wait+release
state.

Provide the required functions and enable the split CPU bringup, which
prepares for parallel bringup, where the bringup of the non-boot CPUs takes
two iterations: One to prepare and wake all APs and the second to wait and
release them. Depending on timing this can eliminate the wait time
completely.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: default avatarMichael Kelley <mikelley@microsoft.com>
Tested-by: default avatarOleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com> # Steam Deck
Link: https://lore.kernel.org/r/20230512205257.133453992@linutronix.de
parent a631be92

arch/x86/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -274,8 +274,8 @@ config X86 
	select HAVE_UNSTABLE_SCHED_CLOCK

	select HAVE_USER_RETURN_NOTIFIER

	select HAVE_GENERIC_VDSO

	select HOTPLUG_CORE_SYNC_FULL		if SMP

	select HOTPLUG_SMT			if SMP

	select HOTPLUG_SPLIT_STARTUP		if SMP

	select IRQ_FORCED_THREADING

	select NEED_PER_CPU_EMBED_FIRST_CHUNK

	select NEED_PER_CPU_PAGE_FIRST_CHUNK

arch/x86/include/asm/smp.h

+2 −7
Original line number Diff line number Diff line
@@ -40,7 +40,7 @@ struct smp_ops { 


	void (*cleanup_dead_cpu)(unsigned cpu);

	void (*poll_sync_state)(void);

	int (*cpu_up)(unsigned cpu, struct task_struct *tidle);

	int (*kick_ap_alive)(unsigned cpu, struct task_struct *tidle);

	int (*cpu_disable)(void);

	void (*cpu_die)(unsigned int cpu);

	void (*play_dead)(void);
@@ -80,11 +80,6 @@ static inline void smp_cpus_done(unsigned int max_cpus) 
	smp_ops.smp_cpus_done(max_cpus);

}



static inline int __cpu_up(unsigned int cpu, struct task_struct *tidle)

{

	return smp_ops.cpu_up(cpu, tidle);

}



static inline int __cpu_disable(void)

{

	return smp_ops.cpu_disable();
@@ -124,7 +119,7 @@ void native_smp_prepare_cpus(unsigned int max_cpus); 
void calculate_max_logical_packages(void);

void native_smp_cpus_done(unsigned int max_cpus);

int common_cpu_up(unsigned int cpunum, struct task_struct *tidle);

int native_cpu_up(unsigned int cpunum, struct task_struct *tidle);

int native_kick_ap(unsigned int cpu, struct task_struct *tidle);

int native_cpu_disable(void);

void __noreturn hlt_play_dead(void);

void native_play_dead(void);

arch/x86/kernel/smp.c

+1 −1
Original line number Diff line number Diff line
@@ -268,7 +268,7 @@ struct smp_ops smp_ops = { 
#endif

	.smp_send_reschedule	= native_smp_send_reschedule,



	.cpu_up			= native_cpu_up,

	.kick_ap_alive		= native_kick_ap,

	.cpu_disable		= native_cpu_disable,

	.play_dead		= native_play_dead,

arch/x86/kernel/smpboot.c

+4 −4
Original line number Diff line number Diff line
@@ -1052,7 +1052,7 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle) 
	return ret;

}



static int native_kick_ap(unsigned int cpu, struct task_struct *tidle)

int native_kick_ap(unsigned int cpu, struct task_struct *tidle)

{

	int apicid = apic->cpu_present_to_apicid(cpu);

	int err;
@@ -1088,15 +1088,15 @@ static int native_kick_ap(unsigned int cpu, struct task_struct *tidle) 
	return err;

}



int native_cpu_up(unsigned int cpu, struct task_struct *tidle)

int arch_cpuhp_kick_ap_alive(unsigned int cpu, struct task_struct *tidle)

{

	return native_kick_ap(cpu, tidle);

	return smp_ops.kick_ap_alive(cpu, tidle);

}



void arch_cpuhp_cleanup_kick_cpu(unsigned int cpu)

{

	/* Cleanup possible dangling ends... */

	if (smp_ops.cpu_up == native_cpu_up && x86_platform.legacy.warm_reset)

	if (smp_ops.kick_ap_alive == native_kick_ap && x86_platform.legacy.warm_reset)

		smpboot_restore_warm_reset_vector();

}

arch/x86/xen/smp_pv.c

+2 −2
Original line number Diff line number Diff line
@@ -314,7 +314,7 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle) 
	return 0;

}



static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)

static int xen_pv_kick_ap(unsigned int cpu, struct task_struct *idle)

{

	int rc;
@@ -438,7 +438,7 @@ static const struct smp_ops xen_smp_ops __initconst = { 
	.smp_prepare_cpus = xen_pv_smp_prepare_cpus,

	.smp_cpus_done = xen_smp_cpus_done,



	.cpu_up = xen_pv_cpu_up,

	.kick_ap_alive = xen_pv_kick_ap,

	.cpu_die = xen_pv_cpu_die,

	.cleanup_dead_cpu = xen_pv_cleanup_dead_cpu,

	.poll_sync_state = xen_pv_poll_sync_state,