diff --git a/[refs] b/[refs]
index 79460fc0b045..d4559c910b4d 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 6d93c64803a5fea84839789aae13290419c62d92
+refs/heads/master: 4c0335526c95d90a1d958e0059f40a5745fc7c5d
diff --git a/trunk/drivers/acpi/processor_idle.c b/trunk/drivers/acpi/processor_idle.c
index 5b6a9865300e..83fd1b6c10c4 100644
--- a/trunk/drivers/acpi/processor_idle.c
+++ b/trunk/drivers/acpi/processor_idle.c
@@ -280,6 +280,16 @@ static void acpi_processor_idle(void)
 
 	cx->usage++;
 
+#ifdef CONFIG_HOTPLUG_CPU
+	/*
+	 * Check for P_LVL2_UP flag before entering C2 and above on
+	 * an SMP system. We do it here instead of doing it at _CST/P_LVL
+	 * detection phase, to work cleanly with logical CPU hotplug.
+	 */
+	if ((cx->type != ACPI_STATE_C1) && (num_online_cpus() > 1) && 
+	    !pr->flags.has_cst && acpi_fadt.plvl2_up)
+		cx->type = ACPI_STATE_C1;
+#endif
 	/*
 	 * Sleep:
 	 * ------
@@ -534,6 +544,15 @@ static int acpi_processor_get_power_info_fadt(struct acpi_processor *pr)
 	pr->power.states[ACPI_STATE_C0].valid = 1;
 	pr->power.states[ACPI_STATE_C1].valid = 1;
 
+#ifndef CONFIG_HOTPLUG_CPU
+	/*
+	 * Check for P_LVL2_UP flag before entering C2 and above on
+	 * an SMP system. 
+	 */
+	if ((num_online_cpus() > 1) && acpi_fadt.plvl2_up)
+		return_VALUE(-ENODEV);
+#endif
+
 	/* determine C2 and C3 address from pblk */
 	pr->power.states[ACPI_STATE_C2].address = pr->pblk + 4;
 	pr->power.states[ACPI_STATE_C3].address = pr->pblk + 5;