[Libvir] PATCH: Fix compat for Xen 3.2.0

[Richard W.M. Jones]

Daniel P. Berrange wrote:
> On Sat, Jan 19, 2008 at 09:21:07PM +0100, Jim Meyering wrote:
>> "Daniel P. Berrange" <berrange at redhat.com> wrote:
>>
>>> Xen 3.2.0 removed the sockets_per_node field from the nodeinfo data returned
>>> by XenD. I previously add compat for this, but got it in the wrong place
>>> so it would most likely end up in a divide-by-zero error. This patch
>>> re-arranges it to be correct.
>>>
>>> diff -rup libvirt-0.4.0.orig/src/xend_internal.c libvirt-0.4.0.new/src/xend_internal.c
>>> --- libvirt-0.4.0.orig/src/xend_internal.c	2007-12-17 18:05:27.000000000 -0500
>>> +++ libvirt-0.4.0.new/src/xend_internal.c	2008-01-18 21:13:30.000000000 -0500
>>> @@ -1907,6 +1907,9 @@ sexpr_to_xend_node_info(struct sexpr *ro
>>>      info->mhz = sexpr_int(root, "node/cpu_mhz");
>>>      info->nodes = sexpr_int(root, "node/nr_nodes");
>>>      info->sockets = sexpr_int(root, "node/sockets_per_node");
>>> +    info->cores = sexpr_int(root, "node/cores_per_socket");
>>> +    info->threads = sexpr_int(root, "node/threads_per_core");
>>> +
>>>      /* Xen 3.2.0 replaces sockets_per_node with 'nr_cpus'.
>>>       * Old Xen calculated sockets_per_node using its internal
>>>       * nr_cpus / (nodes*cores*threads), so fake it ourselves
>>> @@ -1921,8 +1924,6 @@ sexpr_to_xend_node_info(struct sexpr *ro
>>>          if (info->sockets == 0)
>>>              info->sockets = 1;
>>>      }
>>> -    info->cores = sexpr_int(root, "node/cores_per_socket");
>>> -    info->threads = sexpr_int(root, "node/threads_per_core");
>>>      return (0);
>>>  }
>> ACK.
>>
>> Now that you mention divide-by-zero,
>> is there something that guarantees none of the
>> terms in the denominator there is zero?
>>
>>         info->sockets = nr_cpus / (info->nodes * info->cores * info->threads);
> 
> You always have at least 1 numa node, at least 1 core, and at least 1
> hyperthread, so you'd only get a zero in those if there was a bug in the
> Xen hypervisor

.. And that would never happen :-)

Rich.

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