Description of problem:
On IA64, xentop does not work, it causes segmentation fault.

Version-Release number of selected component (if applicable):
xen-3.0.3-55.el5.ia64.rpm
Also, this issue occured even with 3.0.3-44.el5.

How reproducible:
100%

Steps to Reproduce:
1. run xentop on ia64
2.
3.
  
Actual results:
reproduced on ia64 box. It seems this segfault doesn't occur with x86 box.

# gdb /usr/sbin/xentop core.3840
GNU gdb Red Hat Linux (6.5-25.el5_1.1rh)
Copyright (C) 2006 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "ia64-redhat-linux-gnu"...Using host libthread_db
library "/lib/libthread_db.so.1".


warning: Can't read pathname for load map: Input/output error.
Reading symbols from /usr/lib/libxenstore.so.3.0...Reading symbols from
/usr/lib/debug/usr/lib/libxenstore.so.3.0.0.debug...done.
done.
Loaded symbols for /usr/lib/libxenstore.so.3.0
Reading symbols from /usr/lib/libxenctrl.so.3.0...Reading symbols from
/usr/lib/debug/usr/lib/libxenctrl.so.3.0.0.debug...done.
done.
Loaded symbols for /usr/lib/libxenctrl.so.3.0
Reading symbols from /usr/lib/libncurses.so.5...done.
Loaded symbols for /usr/lib/libncurses.so.5
Reading symbols from /lib/libc.so.6.1...done.
Loaded symbols for /lib/libc.so.6.1
Reading symbols from /lib/libpthread.so.0...done.
Loaded symbols for /lib/libpthread.so.0
Reading symbols from /lib/ld-linux-ia64.so.2...done.
Loaded symbols for /lib/ld-linux-ia64.so.2
Reading symbols from /lib/libdl.so.2...done.
Loaded symbols for /lib/libdl.so.2
Core was generated by `xentop'.
Program terminated with signal 11, Segmentation fault.
#0  0x2000000000079940 in xc_physinfo (xc_handle=3, put_info=0x60000fffff9e3558)
at xc_misc.c:87
87                  cpu_to_node[0] = NUMA_NO_NODE;
(gdb) bt
#0  0x2000000000079940 in xc_physinfo (xc_handle=3, put_info=0x60000fffff9e3558)
at xc_misc.c:87
#1  0x40000000000086f0 in xenstat_get_node (handle=0x6000000000010010, flags=15)
at src/xenstat.c:152
#2  0x4000000000004860 in top () at xentop.c:947
#3  0x4000000000006f70 in main (argc=<value optimized out>,
argv=0x60000fffff9e3a38) at xentop.c:1073
#4  0x20000000001636f0 in __libc_start_main () from /lib/libc.so.6.1
#5  0x4000000000002600 in _start ()

Expected results:
xentop works

Additional info:
tools/libxc/xc_misc.c
--------------------------------------
int xc_physinfo(int xc_handle,
               xc_physinfo_t *put_info)
{
   int ret;
   DECLARE_SYSCTL;

   sysctl.cmd = XEN_SYSCTL_physinfo;

   memcpy(&sysctl.u.physinfo, put_info, sizeof(*put_info));

   /*
    * RHEL5 ABI compat.
    * Try new physinfo sysctl first in case HV supports
    * NUMA info, else fallback to original ABI
    */
   if ( (ret = do_sysctl_version(xc_handle, &sysctl,
XEN_SYSCTL_INTERFACE_VERSION+1)) != 0) {
       /* EACCESS indicates old HV version */
       if (errno == EACCES) {
           uint32_t *cpu_to_node;

           if ( (ret = do_sysctl(xc_handle, &sysctl)) != 0 )
               return ret;

           /*
            * Fill in blank NUMA mapping info which old HV can't provide. Only need
            * to set first element since we set max_cpu_id = 0
            */
           memcpy(put_info, &sysctl.u.physinfo, sizeof(*put_info));
           put_info->max_cpu_id = 0;
           get_xen_guest_handle(cpu_to_node, put_info->cpu_to_node);
           cpu_to_node[0] = NUMA_NO_NODE;
           ... snip ...
-----------------------------------------------

(gdb) print put_info->cpu_to_node
$1 = {p = 0x0}

tools/libxc/xen/arch-ia64.h
-----------------------------------------------
#define get_xen_guest_handle(val, hnd)  do { val = (hnd).p; } while (0)
-----------------------------------------------

So, because cpu_to_node is 0, "cpu_to_node[0] = NUMA_NO_NODE" failed.