diff -r 924ce68580ff xen/arch/x86/domain_build.c
--- a/xen/arch/x86/domain_build.c	Wed Dec 08 15:16:00 2010 -0800
+++ b/xen/arch/x86/domain_build.c	Thu Dec 09 20:56:43 2010 -0800
@@ -345,7 +345,7 @@
     paddr_t mpt_alloc;
 
     /* Sanity! */
-    BUG_ON(d->domain_id != 0);
+    BUG_ON(!is_dom0_domain(d));
     BUG_ON(d->vcpu[0] == NULL);
     BUG_ON(v->is_initialised);
 
diff -r 924ce68580ff xen/arch/x86/hvm/i8254.c
--- a/xen/arch/x86/hvm/i8254.c	Wed Dec 08 15:16:00 2010 -0800
+++ b/xen/arch/x86/hvm/i8254.c	Thu Dec 09 20:56:43 2010 -0800
@@ -538,7 +538,7 @@
         .data = data
     };
 
-    if ( (current->domain->domain_id == 0) && dom0_pit_access(&ioreq) )
+    if ( is_dom0_domain(current->domain) && dom0_pit_access(&ioreq) )
     {
         /* nothing to do */;
     }
diff -r 924ce68580ff xen/arch/x86/time.c
--- a/xen/arch/x86/time.c	Wed Dec 08 15:16:00 2010 -0800
+++ b/xen/arch/x86/time.c	Thu Dec 09 20:56:43 2010 -0800
@@ -1777,7 +1777,7 @@
                   uint32_t tsc_mode, uint64_t elapsed_nsec,
                   uint32_t gtsc_khz, uint32_t incarnation)
 {
-    if ( d->domain_id == 0 || d->domain_id == DOMID_INVALID )
+    if ( is_dom0_domain(d) || d->domain_id == DOMID_INVALID )
     {
         d->arch.vtsc = 0;
         return;
@@ -1854,7 +1854,7 @@
                "warp=%lu (count=%lu)\n", tsc_max_warp, tsc_check_count);
     for_each_domain ( d )
     {
-        if ( d->domain_id == 0 && d->arch.tsc_mode == TSC_MODE_DEFAULT )
+        if ( is_dom0_domain(d) && d->arch.tsc_mode == TSC_MODE_DEFAULT )
             continue;
         printk("dom%u%s: mode=%d",d->domain_id,
                 is_hvm_domain(d) ? "(hvm)" : "", d->arch.tsc_mode);
diff -r 924ce68580ff xen/arch/x86/traps.c
--- a/xen/arch/x86/traps.c	Wed Dec 08 15:16:00 2010 -0800
+++ b/xen/arch/x86/traps.c	Thu Dec 09 20:56:43 2010 -0800
@@ -748,7 +748,7 @@
     c = regs->ecx;
     d = regs->edx;
 
-    if ( current->domain->domain_id != 0 )
+    if ( !is_dom0_domain(current->domain) )
     {
         if ( !cpuid_hypervisor_leaves(a, c, &a, &b, &c, &d) )
             domain_cpuid(current->domain, a, c, &a, &b, &c, &d);
@@ -1694,7 +1694,7 @@
 static int is_cpufreq_controller(struct domain *d)
 {
     return ((cpufreq_controller == FREQCTL_dom0_kernel) &&
-            (d->domain_id == 0));
+            is_dom0_domain(d));
 }
 
 static int emulate_privileged_op(struct cpu_user_regs *regs)
@@ -2287,7 +2287,7 @@
         case MSR_IA32_THERM_CONTROL:
             if ( boot_cpu_data.x86_vendor != X86_VENDOR_INTEL )
                 goto fail;
-            if ( (v->domain->domain_id != 0) || !v->domain->is_pinned )
+            if ( !is_dom0_domain(v->domain) || !v->domain->is_pinned )
                 break;
             if ( wrmsr_safe(regs->ecx, msr_content) != 0 )
                 goto fail;
diff -r 924ce68580ff xen/common/domain.c
--- a/xen/common/domain.c	Wed Dec 08 15:16:00 2010 -0800
+++ b/xen/common/domain.c	Thu Dec 09 20:56:43 2010 -0800
@@ -536,7 +536,7 @@
         d->shutdown_code = reason;
     reason = d->shutdown_code;
 
-    if ( d->domain_id == 0 )
+    if ( is_dom0_domain(d) )
         dom0_shutdown(reason);
 
     if ( d->is_shutting_down )
diff -r 924ce68580ff xen/common/sched_sedf.c
--- a/xen/common/sched_sedf.c	Wed Dec 08 15:16:00 2010 -0800
+++ b/xen/common/sched_sedf.c	Thu Dec 09 20:56:43 2010 -0800
@@ -349,7 +349,7 @@
     inf->status      = EXTRA_AWARE | SEDF_ASLEEP;
     inf->extraweight = 1;
 
-    if ( v->domain->domain_id == 0 )
+    if ( is_dom0_domain(v->domain) )
     {
         /* Domain0 gets 75% guaranteed (15ms every 20ms). */
         inf->period    = MILLISECS(20);
diff -r 924ce68580ff xen/common/xenoprof.c
--- a/xen/common/xenoprof.c	Wed Dec 08 15:16:00 2010 -0800
+++ b/xen/common/xenoprof.c	Thu Dec 09 20:56:43 2010 -0800
@@ -605,7 +605,7 @@
 
     xenoprof_init.is_primary = 
         ((xenoprof_primary_profiler == d) ||
-         ((xenoprof_primary_profiler == NULL) && (d->domain_id == 0)));
+         ((xenoprof_primary_profiler == NULL) && is_dom0_domain(d)));
     if ( xenoprof_init.is_primary )
         xenoprof_primary_profiler = current->domain;
 
diff -r 924ce68580ff xen/drivers/char/console.c
--- a/xen/drivers/char/console.c	Wed Dec 08 15:16:00 2010 -0800
+++ b/xen/drivers/char/console.c	Thu Dec 09 20:56:43 2010 -0800
@@ -374,7 +374,7 @@
 
 #ifndef VERBOSE
     /* Only domain 0 may access the emergency console. */
-    if ( current->domain->domain_id != 0 )
+    if ( is_dom0_domain(current->domain) != 0 )
         return -EPERM;
 #endif
 
diff -r 924ce68580ff xen/drivers/passthrough/amd/pci_amd_iommu.c
--- a/xen/drivers/passthrough/amd/pci_amd_iommu.c	Wed Dec 08 15:16:00 2010 -0800
+++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c	Thu Dec 09 20:56:43 2010 -0800
@@ -90,7 +90,7 @@
 
     BUG_ON( !hd->root_table || !hd->paging_mode || !iommu->dev_table.buffer );
 
-    if ( iommu_passthrough && (domain->domain_id == 0) )
+    if ( iommu_passthrough && is_dom0_domain(domain) )
         valid = 0;
 
     /* get device-table entry */
diff -r 924ce68580ff xen/drivers/passthrough/vtd/iommu.c
--- a/xen/drivers/passthrough/vtd/iommu.c	Wed Dec 08 15:16:00 2010 -0800
+++ b/xen/drivers/passthrough/vtd/iommu.c	Thu Dec 09 20:56:43 2010 -0800
@@ -1231,7 +1231,7 @@
         return res;
     }
 
-    if ( iommu_passthrough && (domain->domain_id == 0) )
+    if ( iommu_passthrough && is_dom0_domain(domain) )
     {
         context_set_translation_type(*context, CONTEXT_TT_PASS_THRU);
         agaw = level_to_agaw(iommu->nr_pt_levels);
@@ -1597,7 +1597,7 @@
     int iommu_domid;
 
     /* do nothing if dom0 and iommu supports pass thru */
-    if ( iommu_passthrough && (d->domain_id == 0) )
+    if ( iommu_passthrough && is_dom0_domain(d) )
         return 0;
 
     spin_lock(&hd->mapping_lock);
@@ -1658,7 +1658,7 @@
 static int intel_iommu_unmap_page(struct domain *d, unsigned long gfn)
 {
     /* Do nothing if dom0 and iommu supports pass thru. */
-    if ( iommu_passthrough && (d->domain_id == 0) )
+    if ( iommu_passthrough && is_dom0_domain(d) )
         return 0;
 
     dma_pte_clear_one(d, (paddr_t)gfn << PAGE_SHIFT_4K);
@@ -1764,7 +1764,7 @@
     /* If the device belongs to dom0, and it has RMRR, don't remove it
      * from dom0, because BIOS may use RMRR at booting time.
      */
-    if ( pdev->domain->domain_id == 0 )
+    if ( is_dom0_domain(pdev->domain) )
     {
         for_each_rmrr_device ( rmrr, bdf, i )
         {
diff -r 924ce68580ff xen/drivers/passthrough/vtd/x86/vtd.c
--- a/xen/drivers/passthrough/vtd/x86/vtd.c	Wed Dec 08 15:16:00 2010 -0800
+++ b/xen/drivers/passthrough/vtd/x86/vtd.c	Thu Dec 09 20:56:43 2010 -0800
@@ -131,7 +131,7 @@
     u64 i, j, tmp, max_pfn;
     extern int xen_in_range(unsigned long mfn);
 
-    BUG_ON(d->domain_id != 0);
+    BUG_ON(!is_dom0_domain(d));
 
     max_pfn = max_t(u64, max_page, 0x100000000ull >> PAGE_SHIFT);
 
diff -r 924ce68580ff xen/include/asm-x86/domain.h
--- a/xen/include/asm-x86/domain.h	Wed Dec 08 15:16:00 2010 -0800
+++ b/xen/include/asm-x86/domain.h	Thu Dec 09 20:56:43 2010 -0800
@@ -23,6 +23,8 @@
         d->arch.hvm_domain.irq.callback_via_type == HVMIRQ_callback_vector)
 #define is_hvm_pv_evtchn_vcpu(v) (is_hvm_pv_evtchn_domain(v->domain))
 
+#define is_dom0_domain(d)      ((d)->domain_id == 0)
+
 #define VCPU_TRAP_NMI          1
 #define VCPU_TRAP_MCE          2
 #define VCPU_TRAP_LAST         VCPU_TRAP_MCE