diff --git a/xen/arch/x86/acpi/cpu_idle.c b/xen/arch/x86/acpi/cpu_idle.c
index cdf0f492b4..a4ebbb52e7 100644
--- a/xen/arch/x86/acpi/cpu_idle.c
+++ b/xen/arch/x86/acpi/cpu_idle.c
@@ -351,6 +351,31 @@ static int sched_has_urgent_vcpu(void)
     return atomic_read(&this_cpu(schedule_data).urgent_count);
 }
 
+/*
+ * "AAJ72. EOI Transaction May Not be Sent if Software Enters Core C6 During 
+ * an Interrupt Service Routine"
+ * 
+ * There was an errata with some Core i7 processors that an EOI transaction 
+ * may not be sent if software enters core C6 during an interrupt service 
+ * routine. So we don't enter deep Cx state if there is an EOI pending.
+ */
+bool_t errata_c6_eoi_workaround(void)
+{
+    static bool_t fix_needed = -1;
+
+    if ( unlikely(fix_needed == -1) )
+    {
+        int model = boot_cpu_data.x86_model;
+        fix_needed = (cpu_has_apic && !directed_eoi_enabled &&
+                      (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) &&
+                      (boot_cpu_data.x86 == 6) &&
+                      ((model == 0x1a) || (model == 0x1e) || (model == 0x1f) ||
+                       (model == 0x25) || (model == 0x2c) || (model == 0x2f)));
+    }
+
+    return (fix_needed && cpu_has_pending_apic_eoi());
+}
+
 static void acpi_processor_idle(void)
 {
     struct acpi_processor_power *power = processor_powers[smp_processor_id()];
@@ -401,6 +426,9 @@ static void acpi_processor_idle(void)
         return;
     }
 
+    if ( (cx->type == ACPI_STATE_C3) && errata_c6_eoi_workaround() )
+        cx = power->safe_state;
+
     power->last_state = cx;
 
     /*
diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c
index 7fd967be8a..fa5127e1ac 100644
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -765,6 +765,11 @@ struct pending_eoi {
 static DEFINE_PER_CPU(struct pending_eoi, pending_eoi[NR_DYNAMIC_VECTORS]);
 #define pending_eoi_sp(p) ((p)[NR_DYNAMIC_VECTORS-1].vector)
 
+bool_t cpu_has_pending_apic_eoi(void)
+{
+    return (pending_eoi_sp(this_cpu(pending_eoi)) != 0);
+}
+
 static inline void set_pirq_eoi(struct domain *d, unsigned int irq)
 {
     if ( d->arch.pirq_eoi_map )
diff --git a/xen/include/asm-x86/irq.h b/xen/include/asm-x86/irq.h
index d94647be29..2e80dc948a 100644
--- a/xen/include/asm-x86/irq.h
+++ b/xen/include/asm-x86/irq.h
@@ -147,4 +147,6 @@ void irq_set_affinity(struct irq_desc *, const cpumask_t *mask);
 #define domain_pirq_to_irq(d, pirq) ((d)->arch.pirq_irq[pirq])
 #define domain_irq_to_pirq(d, irq) ((d)->arch.irq_pirq[irq])
 
+bool_t cpu_has_pending_apic_eoi(void);
+
 #endif /* _ASM_HW_IRQ_H */