Re: [Xen-devel] [PATCH] xen/x86: Don't BUG on CPU0 offlining

[Juergen GroÃ]

On 06/28/2017 06:31 PM, Vitaly Kuznetsov wrote:
> Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> writes:
>
> > On Mon, Jun 26, 2017 at 06:39:30PM +0200, Vitaly Kuznetsov wrote:
> > > CONFIG_BOOTPARAM_HOTPLUG_CPU0 allows to offline CPU0 but Xen HVM guests
> > > BUG() in xen_teardown_timer(). Remove the BUG_ON(), this is probably a
> > > leftover from ancient times when CPU0 hotplug was impossible, it works
> > > just fine for HVM.
> > >
> > > Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> >
> > Perhaps:
> >
> > BUG_ON(cpu == 0 && xen_pv_domain());
>
> Linus says no BUG_ONs :-)
>
> xen_pv_cpu_disable() has the following:
>
>      if (cpu == 0)
>              return -EBUSY;
>
> as a protection so we won't get to xen_teardown_timer() but if you think
> additional BUG_ON() protection is justified I'm definitely not against
> adding it.

No, I don't think its needed. This should be handled at the appropriate
level, not down in the timer handling.

So:

Acked-by: Juergen Gross <jgross@xxxxxxxx>


Juergen