x86/amd: Simplify AMD E400 aware idle routine

Reorganize the E400 detection now that we have everything in place:
switch the CPUs to broadcast mode after the LAPIC has been initialized
and remove the facilities that were used previously on the idle path.

Unfortunately static_cpu_has_bug() cannpt be used in the E400 idle routine
because alternatives have been applied when the actual detection happens,
so the static switching does not take effect and the test will stay
false. Use boot_cpu_has_bug() instead which is definitely an improvement
over the RDMSR and the cpumask handling.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20161209182912.2726-5-bp@alien8.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 26 insertions, 49 deletions

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index ced76f1..2c2b55a 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -289,59 +289,33 @@ void stop_this_cpu(void *dummy)
 		halt();
 }
 
-bool amd_e400_c1e_detected;
-EXPORT_SYMBOL(amd_e400_c1e_detected);
-
-static cpumask_var_t amd_e400_c1e_mask;
-
-void amd_e400_remove_cpu(int cpu)
-{
-	if (amd_e400_c1e_mask != NULL)
-		cpumask_clear_cpu(cpu, amd_e400_c1e_mask);
-}
-
 /*
- * AMD Erratum 400 aware idle routine. We check for C1E active in the interrupt
- * pending message MSR. If we detect C1E, then we handle it the same
- * way as C3 power states (local apic timer and TSC stop)
+ * AMD Erratum 400 aware idle routine. We handle it the same way as C3 power
+ * states (local apic timer and TSC stop).
  */
 static void amd_e400_idle(void)
 {
-	if (!amd_e400_c1e_detected) {
-		u32 lo, hi;
-
-		rdmsr(MSR_K8_INT_PENDING_MSG, lo, hi);
-
-		if (lo & K8_INTP_C1E_ACTIVE_MASK) {
-			amd_e400_c1e_detected = true;
-			if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
-				mark_tsc_unstable("TSC halt in AMD C1E");
-			pr_info("System has AMD C1E enabled\n");
-		}
+	/*
+	 * We cannot use static_cpu_has_bug() here because X86_BUG_AMD_APIC_C1E
+	 * gets set after static_cpu_has() places have been converted via
+	 * alternatives.
+	 */
+	if (!boot_cpu_has_bug(X86_BUG_AMD_APIC_C1E)) {
+		default_idle();
+		return;
 	}
 
-	if (amd_e400_c1e_detected) {
-		int cpu = smp_processor_id();
+	tick_broadcast_enter();
 
-		if (!cpumask_test_cpu(cpu, amd_e400_c1e_mask)) {
-			cpumask_set_cpu(cpu, amd_e400_c1e_mask);
-			/* Force broadcast so ACPI can not interfere. */
-			tick_broadcast_force();
-			pr_info("Switch to broadcast mode on CPU%d\n", cpu);
-		}
-		tick_broadcast_enter();
+	default_idle();
 
-		default_idle();
-
-		/*
-		 * The switch back from broadcast mode needs to be
-		 * called with interrupts disabled.
-		 */
-		local_irq_disable();
-		tick_broadcast_exit();
-		local_irq_enable();
-	} else
-		default_idle();
+	/*
+	 * The switch back from broadcast mode needs to be called with
+	 * interrupts disabled.
+	 */
+	local_irq_disable();
+	tick_broadcast_exit();
+	local_irq_enable();
 }
 
 /*
@@ -411,11 +385,14 @@ void select_idle_routine(const struct cpuinfo_x86 *c)
 		x86_idle = default_idle;
 }
 
-void __init init_amd_e400_c1e_mask(void)
+void amd_e400_c1e_apic_setup(void)
 {
-	/* If we're using amd_e400_idle, we need to allocate amd_e400_c1e_mask. */
-	if (x86_idle == amd_e400_idle)
-		zalloc_cpumask_var(&amd_e400_c1e_mask, GFP_KERNEL);
+	if (boot_cpu_has_bug(X86_BUG_AMD_APIC_C1E)) {
+		pr_info("Switch to broadcast mode on CPU%d\n", smp_processor_id());
+		local_irq_disable();
+		tick_broadcast_force();
+		local_irq_enable();
+	}
 }
 
 void __init arch_post_acpi_subsys_init(void)