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x86/idle: Select idle routine only once

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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: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/87edcu6vaq.ffs@tglx
This commit is contained in:
Thomas Gleixner 2024-02-28 23:20:32 +01:00 committed by Borislav Petkov (AMD)
parent 5f75916ec6
commit 35ce64922c
3 changed files with 8 additions and 6 deletions
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2
arch/x86/include/asm/processor.h
View file

@ -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;

4
arch/x86/kernel/cpu/common.c
View file

@ -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.

8
arch/x86/kernel/process.c
View file

@ -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)) {