diff -r 3157b54eb465 xen/arch/x86/domain.c
--- a/xen/arch/x86/domain.c	Thu Jan 04 16:34:19 2007 +0000
+++ b/xen/arch/x86/domain.c	Wed Jan 10 16:51:28 2007 +0800
@@ -713,7 +713,7 @@ void context_switch(struct vcpu *prev, s
 
     local_irq_disable();
 
-    if ( is_hvm_vcpu(prev) )
+    if ( is_hvm_vcpu(prev) && !list_empty(&prev->arch.hvm_vcpu.tm_list) )
         pt_freeze_time(prev);
 
     set_current(next);
diff -r 3157b54eb465 xen/arch/x86/hvm/vioapic.c
--- a/xen/arch/x86/hvm/vioapic.c	Thu Jan 04 16:34:19 2007 +0000
+++ b/xen/arch/x86/hvm/vioapic.c	Wed Jan 10 16:51:28 2007 +0800
@@ -309,6 +309,13 @@ static uint32_t ioapic_get_delivery_bitm
     return mask;
 }
 
+static inline int pit_channel0_enabled(void)
+{
+    PITState *pit = &current->domain->arch.hvm_domain.pl_time.vpit;
+    struct periodic_time *pt = &pit->channels[0].pt;
+    return pt->enabled;
+}
+
 static void vioapic_deliver(struct vioapic *vioapic, int irq)
 {
     uint16_t dest = vioapic->redirtbl[irq].fields.dest_id;
@@ -341,7 +348,7 @@ static void vioapic_deliver(struct vioap
     {
 #ifdef IRQ0_SPECIAL_ROUTING
         /* Force round-robin to pick VCPU 0 */
-        if ( irq == hvm_isa_irq_to_gsi(0) )
+        if ( (irq == hvm_isa_irq_to_gsi(0)) && pit_channel0_enabled() )
         {
             v = vioapic_domain(vioapic)->vcpu[0];
             target = v ? vcpu_vlapic(v) : NULL;
@@ -374,7 +381,7 @@ static void vioapic_deliver(struct vioap
             deliver_bitmask &= ~(1 << bit);
 #ifdef IRQ0_SPECIAL_ROUTING
             /* Do not deliver timer interrupts to VCPU != 0 */
-            if ( irq == hvm_isa_irq_to_gsi(0) )
+            if ( (irq == hvm_isa_irq_to_gsi(0)) && pit_channel0_enabled() )
                 v = vioapic_domain(vioapic)->vcpu[0];
             else
 #endif