Re: [Xen-devel] Wrong number of sockets on IBM x3850 M2

[Gary Grebus <ggrebus@xxxxxxxxxxxxxxx>]

On Thu, 2009-05-07 at 15:34 +0100, Keir Fraser wrote:
> On 07/05/2009 15:06, "Gary Grebus" <ggrebus@xxxxxxxxxxxxxxx> wrote:
> 
> > One of our customers has reported that Xen determines the wrong topology
> > for their machines, identifying them as 6 sockets x 4 cores when in fact
> > they are 4 sockets x 6 cores (Intel(R) Xeon(R) CPU X7460  @ 2.66GHz
> > stepping 01).  The systems are IBM x3850 M2.
> 
> Where is this reported? Via the SYSCTL_physinfo hypercall? 

Right.

> You might have to
> work backwards from the cpu_sibling_map and cpu_core_map values which are
> used there to derive the info returned by that hypercall. The fact that the
> APIC IDs of the CPUs are pretty random and jumbled as the CPUs are brought
> up should not matter.
> 

cpu_sibling_map[] and cpu_core_map[] are built based on the
phys_proc_id[] and cpu_core_id[] arrays, which are set based on
phys_pkg_id(), which is what led me back to the APIC IDs.

I suspect the jumbled IDs come from the BIOS, and that CPUID might
report the real topology, but was hoping someone familiar with the
platform might confirm that.

  /gary 




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