[PATCH v3] xen: domain_update_node_affinity: Bail out early if no VCPUs are allocated

[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

Bail out early if there is d->VCPU is not allocated or VCPU 0 has not been
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

    Changes in v4:
        - Drop the check in common/schedule.c before calling
        domain_update_node_affinity
        - Comment the check in domain_update_node_affinity

    Changes in v3:
        - Change commit message
        - Bail out early rather than modifying the ASSERT
---
 xen/common/domain.c   |    4 ++++
 xen/common/schedule.c |    4 +---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index d7a84cf..ca6174a 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -415,6 +415,10 @@ void domain_update_node_affinity(struct domain *d)
     struct vcpu *v;
     unsigned int cpu;
 
+    /* Do we have vcpus already? If not, no need to update node-affinity */
+    if ( !d->vcpu || !d->vcpu[0] )
+        return;
+
     if ( !zalloc_cpumask_var(&dom_cpumask) )
         return;
     if ( !zalloc_cpumask_var(&dom_cpumask_soft) )
diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index 9a49769..55503e0 100644
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -310,9 +310,7 @@ int sched_move_domain(struct domain *d, struct cpupool *c)
         SCHED_OP(old_ops, free_vdata, vcpudata);
     }
 
-    /* Do we have vcpus already? If not, no need to update node-affinity */
-    if ( d->vcpu )
-        domain_update_node_affinity(d);
+    domain_update_node_affinity(d);
 
     domain_unpause(d);
 
-- 
1.7.10.4