Re: [Xen-devel] dom0less + sched=null => broken in staging

[Dario Faggioli <dfaggioli@xxxxxxxx>]

On Wed, 2019-08-07 at 11:22 -0700, Stefano Stabellini wrote:
> Hi Dario, George,
> 
> Dom0less with sched=null is broken on staging, it simply hangs soon
> after Xen is finished loading things. My impression is that vcpus are
> not actually started. I did a git bisection and it pointed to:
> 
> commit d545f1d6c2519a183ed631cfca7aff0baf29fde5 (refs/bisect/bad)
> Author: Dario Faggioli <dfaggioli@xxxxxxxx>
> Date:   Mon Aug 5 11:50:55 2019 +0100
> 
>     xen: sched: deal with vCPUs being or becoming online or offline
>     
> Any ideas?
> 
Ok, I've done some basic testing, and inspected the code again, and
honestly I am not finding anything really suspicious.

Of course, I'm not really testing dom0less, and I'm not sure I can
easily do that.

Can you help me with this, e.g., by providing some more info and, if
possible, logs?

E.g., you say boot stops after Xen loading. Is there a bootlog that we
can see (ideally from a debug build, and with "loglvl=all
guest_loglvl=all")?

Does the system respond to debug-keys? If yes, the log after triggering
the 'r' debug-key would be useful.

These patches are about vcpus going offline and online... does dom0less
play with vcpu onffline/online in any way?

I've put together a debug patch (attached), focusing on what the
mentioned commit does, but it's nothing more than a shot in the dark,
for now...

Thanks and 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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