[xen staging] xen/domain: Introduce arch_init_idle_domain()

[patchbot@xxxxxxx]

commit 694ce812e7cb643236e8e677aca763c5f2aa4f4b
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Thu Jul 18 20:54:05 2024 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Wed Jul 31 11:14:50 2024 +0100

    xen/domain: Introduce arch_init_idle_domain()
    
    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>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 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 7b47696dd3..f1d54845ec 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -686,6 +686,9 @@ 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 2dcd1d1a4f..90666576c2 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
--
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