Re: [Xen-devel] [PATCH] x86: correct socket_cpumask allocation for AP

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Wed, 2015-07-08 at 16:38 +0100, Jan Beulich wrote:
> >>> On 08.07.15 at 17:11, <dario.faggioli@xxxxxxxxxx> wrote:
> > On Wed, 2015-07-08 at 13:38 +0100, Jan Beulich wrote:
> >> >>> On 08.07.15 at 11:36, <chao.p.peng@xxxxxxxxxxxxxxx> wrote:
> >> > @@ -84,11 +85,21 @@ void *stack_base[NR_CPUS];
> >> >  static void smp_store_cpu_info(int id)
> >> >  {
> >> >      struct cpuinfo_x86 *c = cpu_data + id;
> >> > +    unsigned int socket;
> >> >  
> >> >      *c = boot_cpu_data;
> >> >      if ( id != 0 )
> >> > +    {
> >> >          identify_cpu(c);
> >> >  
> >> > +        socket = cpu_to_socket(id);
> >> > +        if ( !socket_cpumask[socket] )
> >> > +        {
> >> > +            socket_cpumask[socket] = secondary_socket_cpumask;
> >> > +            secondary_socket_cpumask = NULL;
> >> 
> >> I don't think this will build with small enough NR_CPUS.
> >>
> > And it *does* *not* fix the issue on my box.
> 
> I.e. bad analysis (albeit it seemed correct to me)
>
Same here, and in fact I triple checked that I had the patch really
applied... and, yes, it is, and it's still crashing, with the same
(reported) dump as the one we find in Osstest's failure, as reported by
Ian.

>  _and_ new code not tested. 
>
Looking another time, both me and Osstest are probably seeing a
different issue, than the one Boris is facing. I don't see Boris' Oops,
so I can't be sure, but in my case, this is happening in
set_cpu_sibling_map(), called from smp_prepare_cpus() on the boot CPU,
not during secondary CPUs bringup.

I think it has to do with the fact that I've got CPU #0 on socket #1,
while Boris' (and perhaps Chao's too) test box have it on socket #0.

I'd be happy to test patches on my box, if that helps (although, I'm
about to leave right now, so that will be tomorrow).

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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