Re: [PATCH] xen: domain_update_node_affinity: Correct the ASSERT

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 25/07/14 16:30, Julien Grall wrote:
> 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));

You don't actually care for the vcpu pointers themselves.  You only care
whether the domain has vcpus.

d->max_vcpus == 0 is a more appropriate check.

~Andrew

>          /* And compute the intersection between hard, online and soft */
>          cpumask_and(dom_cpumask_soft, dom_cpumask_soft, dom_cpumask);
>