On Mon, 2021-08-09 at 18:35 +0100, Julien Grall wrote: > On 09/08/2021 17:19, Ahmed, Daniele wrote: > > Hi all, > > Hi Daniele, > Hello everyone from me as well,
> Thank you for the report!
>
Indeed. :-)
>
> The ASSERT() is triggered because the pCPU was already assigned to
> one
> of the dom0 vCPU. This problem is happening regardless whether there
> is
> free pCPU.
>
Right. Can we raise the appropriate log level, so that we can see these
messages:
dprintk(XENLOG_G_INFO, "%d <-- %pdv%d\n", cpu, unit->domain, unit->unit_id);
(and then see a full `xl dmesg`, or even better, a serial console dump,
since we crash! :-P)
> I have added some debugging in sched_set_res():
>
> diff --git a/xen/common/sched/private.h b/xen/common/sched/private.h
> index a870320146ef..2355f531dc13 100644
> --- a/xen/common/sched/private.h
> +++ b/xen/common/sched/private.h
> @@ -150,6 +150,10 @@ static inline void sched_set_res(struct
> sched_unit
> *unit,
> unsigned int cpu = cpumask_first(res->cpus);
> struct vcpu *v;
>
> + printk("%s: res->master_cpu %u unit %p %pd %pv\n", __func__,
> + res->master_cpu, unit, unit->domain, unit->vcpu_list);
> + WARN();
> +
> for_each_sched_unit_vcpu ( unit, v )
> {
> ASSERT(cpu < nr_cpu_ids);
>
> This traced the problem to null_unit_migrate():
>
> (XEN) sched_set_res: res->master_cpu 0 unit ffff830200887f00 d1 d1v0
> (XEN) Xen WARN at private.h:155
> (XEN) ----[ Xen-4.16-unstable x86_64 debug=y Tainted: C ]----
> (XEN) CPU: 1
> (XEN) RIP: e008:[<ffff82d04023fd9f>]
> core.c#sched_set_res+0x5b/0xc6
> [...]
> (XEN) Xen call trace:
> (XEN) [<ffff82d04023fd9f>] R core.c#sched_set_res+0x5b/0xc6
> (XEN) [<ffff82d040241614>] F sched_init_vcpu+0x3dc/0x5d7
> (XEN) [<ffff82d04020527d>] F vcpu_create+0xfb/0x37a
> (XEN) [<ffff82d040238dd9>] F do_domctl+0xac0/0x184a
> (XEN) [<ffff82d04030d8bc>] F pv_hypercall+0x10d/0x2b8
> (XEN) [<ffff82d04038829d>] F lstar_enter+0x12d/0x140
> (XEN)
>
So, it's entirely possible that I'm missing something obvious here, but
what it is that is making you think that we're in null_unit_migrate() ?
Does that come from a different instance of this WARN() ?
Regards
--
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
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<<This happens because _I_ choose it to happen!>> (Raistlin Majere)
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