Xen devel - Feb 2007 - A strange behavior by the xm vcpu-pin command

Hi all,

I found a strange behavior by the xm vcpu-pin command. 
My machine has two physical CPUs. 
When I specified "64" to physical CPU number, the CPU affinity was
"0".
When I specified "65" to physical CPU number, the CPU affinity was
"1".
When I specified "66" to physical CPU number, the xm vcpu-pin command 
was error. 

# xm vcpu-list vm1
Name                              ID  VCPU   CPU State   Time(s) CPU Affinity
vm1                                2     0     1   ---      19.0 any cpu
# xm vcpu-pin vm1 0 64
# xm vcpu-list vm1
Name                              ID  VCPU   CPU State   Time(s) CPU Affinity
vm1                                2     0     0   -b-      21.0 0
# xm vcpu-pin vm1 0 65
# xm vcpu-list vm1
Name                              ID  VCPU   CPU State   Time(s) CPU Affinity
vm1                                2     0     1   -b-      22.6 1
# xm vcpu-pin vm1 0 66
Error: (22, ''Invalid argument'')
Usage: xm vcpu-pin <Domain> <VCPU> <CPUs>

Set which CPUs a VCPU can use.
# xm vcpu-list vm1
Name                              ID  VCPU   CPU State   Time(s) CPU Affinity
vm1                                2     0     1   -b-      24.6 1


I thought that the cause is in line 201 of pyxc_vcpu_setaffinity(). 
But I think that the value of cpumap is 0 when shifting by the value of 
64 or more. If the valus of cpumap is 0, I think that the strange 
behavior does not occur. 
Where is a true cause?

182 static PyObject *pyxc_vcpu_setaffinity(XcObject *self,
183                                        PyObject *args,
184                                        PyObject *kwds)
185 {
186     uint32_t dom;
187     int vcpu = 0, i;
188     uint64_t  cpumap = ~0ULL;
189     PyObject *cpulist = NULL;
190 
191     static char *kwd_list[] = { "domid", "vcpu",
"cpumap", NULL };
192 
193     if ( !PyArg_ParseTupleAndKeywords(args, kwds, "i|iO",
kwd_list,
194                                       &dom, &vcpu, &cpulist) )
195         return NULL;
196 
197     if ( (cpulist != NULL) && PyList_Check(cpulist) )
198     {
199         cpumap = 0ULL;
200         for ( i = 0; i < PyList_Size(cpulist); i++ ) 
201             cpumap |= (uint64_t)1 <<
PyInt_AsLong(PyList_GetItem(cpulist, i));
202     }
203   
204     if ( xc_vcpu_setaffinity(self->xc_handle, dom, vcpu, cpumap) != 0 )
205         return pyxc_error_to_exception();
206     
207     Py_INCREF(zero);
208     return zero;
209 }


Best regards,
 Kan



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