Re: [PATCH v8 01/13] x86: add socket_cpumask

[Chao Peng <chao.p.peng@linux.intel.com>]

On Thu, May 28, 2015 at 01:38:05PM +0100, Jan Beulich wrote:
> >>> On 21.05.15 at 10:41, <chao.p.peng@linux.intel.com> wrote:
> > --- a/xen/arch/x86/mpparse.c
> > +++ b/xen/arch/x86/mpparse.c
> > @@ -87,6 +87,18 @@ void __init set_nr_cpu_ids(unsigned int max_cpus)
> >  #endif
> >  }
> >  
> > +void __init set_nr_sockets(void)
> > +{
> > +    unsigned int cpus = bitmap_weight(phys_cpu_present_map.mask,
> > +                                      boot_cpu_data.x86_max_cores *
> > +                                      boot_cpu_data.x86_num_siblings);
> 
> How did you come to this expression for the bitmap size? I.e.
> why not simply physids_weight(phys_cpu_present_map)?

physids_weight(phys_cpu_present_map) gives me cpus for all sockets.
While here the 'cpus' is actually _cpus_per_socket_. I used the max
possible cpus indicated in cpuid as the upper bound so bitmap_weight()
returns the actual available cpus on socket 0.

> 
> > +
> > +    if ( cpus == 0 )
> > +        cpus = 1;
> > +
> > +    nr_sockets = DIV_ROUND_UP(num_processors + disabled_cpus, cpus);
> > +}
> 
> Is there a reason why this can't just be added to the end of the
> immediately preceding set_nr_cpu_ids()?

You mean the declaration or invocation? If the former I have no special
reason for it (e.g. I can change it).

> > +/* Representing HT and core siblings in each socket */
> > +extern cpumask_var_t *socket_cpumask;
> 
> Comment style.

Ah, stop is missing here.

Chao