[PATCH] xen: domain_update_node_affinity: Correct the ASSERT

[Julien Grall <julien.grall@linaro.org>]

The commit "move domain to cpupool0 before destroying it" make Xen crashes
when a domain is destroyed with d->vcpus allocated but no VCPU initialized.

Assertion '!cpumask_empty(dom_cpumask)' failed at domain.c:452
Xen call trace:
    [<00207bd8>] domain_update_node_affinity+0x10c/0x238 (PC)
    [<00000004>] 00000004 (LR)
    [<00226870>] sched_move_domain+0x3cc/0x42c
    [<0020925c>] domain_kill+0xc8/0x178
    [<00206a0c>] do_domctl+0xaac/0x15e4
    [<002529c0>] do_trap_hypervisor+0xc5c/0xf94
    [<002559f0>] return_from_trap+0/0x4

Fix the ASSERT to check if d->vcpu is allocated and VCPU 0 is initialized.

Signed-off-by: Julien Grall <julien.grall@linaro.org>
Cc: George Dunlap <george.dunlap@citrix.com>
Cc: Dario Faggioli <dario.faggioli@citrix.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Keir Fraser <keir@xen.org>
Cc: Tim Deegan <tim@xen.org>

---
    This patch should be backported to Xen 4.4
---
 xen/common/domain.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index d7a84cf..188b769 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -449,7 +449,7 @@ void domain_update_node_affinity(struct domain *d)
         }
         /* Filter out non-online cpus */
         cpumask_and(dom_cpumask, dom_cpumask, online);
-        ASSERT(!cpumask_empty(dom_cpumask));
+        ASSERT( !d->vcpu || !d->vcpu[0] || !cpumask_empty(dom_cpumask));
         /* And compute the intersection between hard, online and soft */
         cpumask_and(dom_cpumask_soft, dom_cpumask_soft, dom_cpumask);
 
-- 
1.7.10.4