[PATCH] xen/sched: fix sched_move_domain() for domain without vcpus

[Juergen Gross <jgross@xxxxxxxx>]

In case a domain is created with a cpupool other than Pool-0 specified
it will be moved to that cpupool before any vcpus are allocated.

This will lead to a NULL pointer dereference in sched_move_domain().

Fix that by tolerating vcpus not being allocated yet.

Fixes: 70fadc41635b9b6 ("xen/cpupool: support moving domain between cpupools 
with different granularity")
Reported-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/common/sched/core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/xen/common/sched/core.c b/xen/common/sched/core.c
index 8d178baf3d..79c9100680 100644
--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -671,6 +671,10 @@ int sched_move_domain(struct domain *d, struct cpupool *c)
 
     for ( unit_idx = 0; unit_idx < n_units; unit_idx++ )
     {
+        /* Special case for move at domain creation time. */
+        if ( !d->vcpu[unit_idx * gran] )
+            break;
+
         unit = sched_alloc_unit_mem();
         if ( unit )
         {
-- 
2.26.2