[PATCH 1/4] xen/domain: Introduce arch_init_idle_domain()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

The idle domain causes a large amount of complexity in domain_create() because
of x86's need to initialise d->arch.ctxt_switch in arch_domain_create().

In order to address this, introduce an optional hook to perform extra
initialisation of the idle domain.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Julien Grall <julien@xxxxxxx>
CC: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
CC: Bertrand Marquis <bertrand.marquis@xxxxxxx>
CC: Michal Orzel <michal.orzel@xxxxxxx>
CC: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
 xen/common/domain.c     | 3 +++
 xen/include/xen/sched.h | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index fb262dcec919..e312c820d641 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -685,6 +685,9 @@ struct domain *domain_create(domid_t domid,
 
     rangeset_domain_initialise(d);
 
+    if ( is_idle_domain(d) )
+        arch_init_idle_domain(d);
+
     /* DOMID_{XEN,IO,etc} (other than IDLE) are sufficiently constructed. */
     if ( is_system_domain(d) && !is_idle_domain(d) )
         return d;
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 2dcd1d1a4f8a..90666576c2f8 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -728,6 +728,11 @@ struct domain *domain_create(domid_t domid,
                              struct xen_domctl_createdomain *config,
                              unsigned int flags);
 
+#ifndef arch_init_idle_domain
+/* Optional, if there's any construction necessary for DOMID_IDLE */
+static inline void arch_init_idle_domain(struct domain *d) {}
+#endif
+
 /*
  * rcu_lock_domain_by_id() is more efficient than get_domain_by_id().
  * This is the preferred function if the returned domain reference
-- 
2.39.2