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

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

On 25/07/14 16:48, Julien Grall wrote:
> On 07/25/2014 04:44 PM, Andrew Cooper wrote:
>> 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.
> Actually no... max_vcpus has been set before Xen is allocating
> alloc_vcpu (see DOMCTL_max_vpus in common common/domctl.c).
>
> So if Xen fails to allocate VCPU0, the hypervisor will still crash when
> the domain is killed.
>
> Regards,
>

Ah yes - I had mis-remembered the problem at hand.  Sorry for the noise.

~Andrew