Re: [Xen-devel] [PATCH 49/60] xen/sched: reject switching smt on/off with core scheduling active

[Dario Faggioli <dfaggioli@xxxxxxxx>]

On Tue, 2019-05-28 at 13:52 +0200, Juergen Gross wrote:
> On 28/05/2019 13:44, Jan Beulich wrote:
> > > > > On 28.05.19 at 12:33, <jgross@xxxxxxxx> wrote:
> > > --- a/xen/arch/x86/sysctl.c
> > > +++ b/xen/arch/x86/sysctl.c
> > > @@ -200,7 +200,8 @@ long arch_do_sysctl(
> > >  
> > >          case XEN_SYSCTL_CPU_HOTPLUG_SMT_ENABLE:
> > >          case XEN_SYSCTL_CPU_HOTPLUG_SMT_DISABLE:
> > > -            if ( !cpu_has_htt || boot_cpu_data.x86_num_siblings
> > > < 2 )
> > > +            if ( !cpu_has_htt || boot_cpu_data.x86_num_siblings
> > > < 2 ||
> > > +                 sched_disable_smt_switching )
> > >              {
> > >                  ret = -EOPNOTSUPP;
> > >                  break;
> > 
> > I'm not convinced -EOPNOTSUPP is an appropriate error code for
> > this new case. -EPERM, -EACCES, or -EIO would all seem more
> > appropriate to me (and perhaps there are further ones).
> 
> I think -EIO or -EBUSY would be the best fit.
> 
I agree, with mild preference for EBUSY.

Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
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