Re: [Xen-devel] [PATCH v7 01/14] x86: add socket_to_cpumask

[Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>]

On Tue, May 19, 2015 at 07:28:49AM +0100, Jan Beulich wrote:
> >>> On 19.05.15 at 08:12, <chao.p.peng@xxxxxxxxxxxxxxx> wrote:
> > On Mon, May 18, 2015 at 02:21:40PM +0100, Jan Beulich wrote:
> >> >>> On 08.05.15 at 10:56, <chao.p.peng@xxxxxxxxxxxxxxx> wrote:
> >> > @@ -112,6 +115,8 @@ static int __devinit MP_processor_info_x(struct 
> >> > mpc_config_processor *m,
> >> >  {
> >> >          int ver, apicid, cpu = 0;
> >> >          
> >> > +        total_cpus++;
> >> > +
> >> >          if (!(m->mpc_cpuflag & CPU_ENABLED)) {
> >> >                  if (!hotplug)
> >> >                          ++disabled_cpus;
> >> 
> >> Is there a reason you can't use disabled_cpus and avoid adding yet
> >> another variable?
> > 
> > The problem is not with disabled_cpus but with num_processors, which
> > does not keep the original detected cpus in current code.
> > Hence 'total_cpus = disabled_cpus + num_processors' may not be correct
> > in some cases.
> 
> Please be more specific about when this is a problem (I do note that
> I'm aware that the equation will not always hold, but during my
> inspection while reviewing your change I didn't see that this would
> ever become problematic).

What I really need is the original cpu count enumerated from MADT. If
not introduce total_cpus then the only way getting it AFAICS is
'disabled_cpus + num_processors'.

The problem is that MP_processor_info_x() have some earlier returns
before increasing num_processors. In those cases, the cpu detected will
neither counted to disabled_cpus nor num_processors, which means
'disabled_cpus + num_processors' is potentially small than what I need.

Chao

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