Commit 35ce6492 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Borislav Petkov (AMD)
Browse files

x86/idle: Select idle routine only once 



The idle routine selection is done on every CPU bringup operation and
has a guard in place which is effective after the first invocation,
which is a pointless exercise.

Invoke it once on the boot CPU and mark the related functions __init.
The guard check has to stay as xen_set_default_idle() runs early.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/87edcu6vaq.ffs@tglx
parent 5f75916e

arch/x86/include/asm/processor.h

+1 −1
Original line number Diff line number Diff line
@@ -558,7 +558,7 @@ static inline void load_sp0(unsigned long sp0) 


unsigned long __get_wchan(struct task_struct *p);



extern void select_idle_routine(const struct cpuinfo_x86 *c);

extern void select_idle_routine(void);

extern void amd_e400_c1e_apic_setup(void);



extern unsigned long		boot_option_idle_override;

arch/x86/kernel/cpu/common.c

+2 −2
Original line number Diff line number Diff line
@@ -1938,8 +1938,6 @@ static void identify_cpu(struct cpuinfo_x86 *c) 
	/* Init Machine Check Exception if available. */

	mcheck_cpu_init(c);



	select_idle_routine(c);



#ifdef CONFIG_NUMA

	numa_add_cpu(smp_processor_id());

#endif
@@ -2344,6 +2342,8 @@ void __init arch_cpu_finalize_init(void) 
{

	identify_boot_cpu();



	select_idle_routine();



	/*

	 * identify_boot_cpu() initialized SMT support information, let the

	 * core code know.

arch/x86/kernel/process.c

+5 −3
Original line number Diff line number Diff line
@@ -853,8 +853,9 @@ void __noreturn stop_this_cpu(void *dummy) 
 * Do not prefer MWAIT if MONITOR instruction has a bug or idle=nomwait

 * is passed to kernel commandline parameter.

 */

static bool prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c)

static __init bool prefer_mwait_c1_over_halt(void)

{

	const struct cpuinfo_x86 *c = &boot_cpu_data;

	u32 eax, ebx, ecx, edx;



	/* If override is enforced on the command line, fall back to HALT. */
@@ -908,7 +909,7 @@ static __cpuidle void mwait_idle(void) 
	__current_clr_polling();

}



void select_idle_routine(const struct cpuinfo_x86 *c)

void __init select_idle_routine(void)

{

	if (boot_option_idle_override == IDLE_POLL) {

		if (IS_ENABLED(CONFIG_SMP) && smp_num_siblings > 1)
@@ -916,10 +917,11 @@ void select_idle_routine(const struct cpuinfo_x86 *c) 
		return;

	}



	/* Required to guard against xen_set_default_idle() */

	if (x86_idle_set())

		return;



	if (prefer_mwait_c1_over_halt(c)) {

	if (prefer_mwait_c1_over_halt()) {

		pr_info("using mwait in idle threads\n");

		static_call_update(x86_idle, mwait_idle);

	} else if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) {