x86/idle: Replace 'x86_idle' function pointer with a static_call

Typical boot time setup; no need to suffer an indirect call for that.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20230112195539.453613251@infradead.org

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 40d156a31676e66dd0f3c694f4ea670d67742c38..8481fbefe2829838420d262fc273c4ff57837652 100644 (file)
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -24,6 +24,7 @@
 #include <linux/cpuidle.h>
 #include <linux/acpi.h>
 #include <linux/elf-randomize.h>
+#include <linux/static_call.h>
 #include <trace/events/power.h>
 #include <linux/hw_breakpoint.h>
 #include <asm/cpu.h>
@@ -694,7 +695,23 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p)
 unsigned long boot_option_idle_override = IDLE_NO_OVERRIDE;
 EXPORT_SYMBOL(boot_option_idle_override);
 
-static void (*x86_idle)(void);
+/*
+ * We use this if we don't have any better idle routine..
+ */
+void __cpuidle default_idle(void)
+{
+       raw_safe_halt();
+}
+#if defined(CONFIG_APM_MODULE) || defined(CONFIG_HALTPOLL_CPUIDLE_MODULE)
+EXPORT_SYMBOL(default_idle);
+#endif
+
+DEFINE_STATIC_CALL_NULL(x86_idle, default_idle);
+
+static bool x86_idle_set(void)
+{
+       return !!static_call_query(x86_idle);
+}
 
 #ifndef CONFIG_SMP
 static inline void play_dead(void)
@@ -717,28 +734,17 @@ void arch_cpu_idle_dead(void)
 /*
  * Called from the generic idle code.
  */
-void arch_cpu_idle(void)
-{
-       x86_idle();
-}
-
-/*
- * We use this if we don't have any better idle routine..
- */
-void __cpuidle default_idle(void)
+void __cpuidle arch_cpu_idle(void)
 {
-       raw_safe_halt();
+       static_call(x86_idle)();
 }
-#if defined(CONFIG_APM_MODULE) || defined(CONFIG_HALTPOLL_CPUIDLE_MODULE)
-EXPORT_SYMBOL(default_idle);
-#endif
 
 #ifdef CONFIG_XEN
 bool xen_set_default_idle(void)
 {
-       bool ret = !!x86_idle;
+       bool ret = x86_idle_set();
 
-       x86_idle = default_idle;
+       static_call_update(x86_idle, default_idle);
 
        return ret;
 }
@@ -880,20 +886,20 @@ void select_idle_routine(const struct cpuinfo_x86 *c)
        if (boot_option_idle_override == IDLE_POLL && smp_num_siblings > 1)
                pr_warn_once("WARNING: polling idle and HT enabled, performance may degrade\n");
 #endif
-       if (x86_idle || boot_option_idle_override == IDLE_POLL)
+       if (x86_idle_set() || boot_option_idle_override == IDLE_POLL)
                return;
 
        if (boot_cpu_has_bug(X86_BUG_AMD_E400)) {
                pr_info("using AMD E400 aware idle routine\n");
-               x86_idle = amd_e400_idle;
+               static_call_update(x86_idle, amd_e400_idle);
        } else if (prefer_mwait_c1_over_halt(c)) {
                pr_info("using mwait in idle threads\n");
-               x86_idle = mwait_idle;
+               static_call_update(x86_idle, mwait_idle);
        } else if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) {
                pr_info("using TDX aware idle routine\n");
-               x86_idle = tdx_safe_halt;
+               static_call_update(x86_idle, tdx_safe_halt);
        } else
-               x86_idle = default_idle;
+               static_call_update(x86_idle, default_idle);
 }
 
 void amd_e400_c1e_apic_setup(void)
@@ -946,7 +952,7 @@ static int __init idle_setup(char *str)
                 * To continue to load the CPU idle driver, don't touch
                 * the boot_option_idle_override.
                 */
-               x86_idle = default_idle;
+               static_call_update(x86_idle, default_idle);
                boot_option_idle_override = IDLE_HALT;
        } else if (!strcmp(str, "nomwait")) {
                /*