x86/mtrr: Avoid repeated save of MTRRs on boot-time CPU bringup

There's no need to repeatedly save the BSP's MTRRs for each AP being
brought up at boot time. And no need to use smp_call_function_single()
even for the one time they do need to be saved.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Usama Arif <usama.arif@bytedance.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

arch/x86/kernel/cpu/mtrr/mtrr.c

@@ -721,11 +721,20 @@ void __init mtrr_bp_init(void)
  */
 void mtrr_save_state(void)
 {
+	static bool mtrr_saved;
 	int first_cpu;
 
 	if (!mtrr_enabled())
 		return;
 
+	if (system_state < SYSTEM_RUNNING) {
+		if (!mtrr_saved) {
+			mtrr_save_fixed_ranges(NULL);
+			mtrr_saved = true;
+		}
+		return;
+	}
+
 	first_cpu = cpumask_first(cpu_online_mask);
 	smp_call_function_single(first_cpu, mtrr_save_fixed_ranges, NULL, 1);
 }