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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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8
arch/x86/kernel/process.c
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@@ -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)) {