[RFC 1/6] dom0: replace explict zero checks

["Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>]

A legacy concept is that the initial domain will have a domain id of zero. As a
result there are places where a check that a domain is the inital domain is
determined by an explicit check that the domid is zero.

This commit seeks to abstract this check into a function call and replace all
check locations with the function call.

Signed-off-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
---
 xen/common/domain.c         | 4 ++--
 xen/common/sched/arinc653.c | 2 +-
 xen/common/sched/core.c     | 4 ++--
 xen/include/xen/sched.h     | 7 +++++++
 4 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index 304aa04fa6..8fb3c052f5 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -309,7 +309,7 @@ static int late_hwdom_init(struct domain *d)
     struct domain *dom0;
     int rv;
 
-    if ( d != hardware_domain || d->domain_id == 0 )
+    if ( d != hardware_domain || is_initial_domain(d) )
         return 0;
 
     rv = xsm_init_hardware_domain(XSM_HOOK, d);
@@ -612,7 +612,7 @@ struct domain *domain_create(domid_t domid,
     d->is_privileged = flags & CDF_privileged;
 
     /* Sort out our idea of is_hardware_domain(). */
-    if ( domid == 0 || domid == hardware_domid )
+    if ( is_initial_domain(d) || domid == hardware_domid )
     {
         if ( hardware_domid < 0 || hardware_domid >= DOMID_FIRST_RESERVED )
             panic("The value of hardware_dom must be a valid domain ID\n");
diff --git a/xen/common/sched/arinc653.c b/xen/common/sched/arinc653.c
index a82c0d7314..31e8270af3 100644
--- a/xen/common/sched/arinc653.c
+++ b/xen/common/sched/arinc653.c
@@ -404,7 +404,7 @@ a653sched_alloc_udata(const struct scheduler *ops, struct 
sched_unit *unit,
      * Add every one of dom0's units to the schedule, as long as there are
      * slots available.
      */
-    if ( unit->domain->domain_id == 0 )
+    if ( is_initial_domain(unit->domain) )
     {
         entry = sched_priv->num_schedule_entries;
 
diff --git a/xen/common/sched/core.c b/xen/common/sched/core.c
index 022f548652..210ad30f94 100644
--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -585,7 +585,7 @@ int sched_init_vcpu(struct vcpu *v)
          */
         sched_set_affinity(unit, cpumask_of(0), cpumask_of(0));
     }
-    else if ( d->domain_id == 0 && opt_dom0_vcpus_pin )
+    else if ( is_initial_domain(d) && opt_dom0_vcpus_pin )
     {
         /*
          * If dom0_vcpus_pin is specified, dom0 vCPUs are pinned 1:1 to
@@ -594,7 +594,7 @@ int sched_init_vcpu(struct vcpu *v)
         sched_set_affinity(unit, cpumask_of(processor), &cpumask_all);
     }
 #ifdef CONFIG_X86
-    else if ( d->domain_id == 0 )
+    else if ( is_initial_domain(d) )
     {
         /*
          * In absence of dom0_vcpus_pin instead, the hard and soft affinity of
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 854f3e32c0..a9276a7bed 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -1058,6 +1058,13 @@ void scheduler_disable(void);
 void watchdog_domain_init(struct domain *d);
 void watchdog_domain_destroy(struct domain *d);
 
+static always_inline bool is_initial_domain(const struct domain *d)
+{
+    static int init_domain_id = 0;
+
+    return d->domain_id == init_domain_id;
+}
+
 /*
  * Use this check when the following are both true:
  *  - Using this feature or interface requires full access to the hardware
-- 
2.20.1