[root@dell-per730-58 ~]# rpm -qa | grep libvirt-4
libvirt-4.5.0-10.virtcov.el7_6.6.x86_64


1. Code update to date
root@yisun ~/libvirt-rhel/src  ## git branch
* (detached from origin/rhel-7.6)
  rhel-7.7
root@yisun ~/libvirt-rhel/src  ## cat util/virrandom.c | grep "uint64_t virRandomBits(int nbits)" -A15
uint64_t virRandomBits(int nbits)
{
    uint64_t ret = 0;

    if (virRandomBytes((unsigned char *) &ret, sizeof(ret)) < 0) {
        /* You're already hosed, so this particular non-random value
         * isn't any worse.  */
        return 0;
    }

    if (nbits < 64)
        ret &= (1ULL << nbits) - 1;

    return ret;
}


2. Try the random number generator with scenario as comment 0
[root@dell-per730-58 ~]# cat vhba.xml 
<device><capability type="scsi_host"><capability type="fc_host"><wwnn /><wwpn /></capability></capability><parent>scsi_host11</parent></device>


[root@dell-per730-58 ~]# for i in {63..163}; do virsh nodedev-create vhba.xml >> /dev/null 2>&1; echo $i; virsh nodedev-dumpxml scsi_host$i | egrep "wwpn|wwnn"; done
63
      <wwnn>5001a4a6c3760b1f</wwnn>
      <wwpn>5001a4a985482b07</wwpn>
64
      <wwnn>5001a4a77396629a</wwnn>
      <wwpn>5001a4a4fb2a6084</wwpn>
65
      <wwnn>5001a4adf0bdaccb</wwnn>
      <wwpn>5001a4a23b1f2ada</wwpn>
66
      <wwnn>5001a4a00b4e2197</wwnn>
      <wwpn>5001a4a30058f906</wwpn>
...
162
      <wwnn>5001a4a20c9321d3</wwnn>
      <wwpn>5001a4af5f03bcce</wwpn>
163
      <wwnn>5001a4a676ad0673</wwnn>
      <wwpn>5001a4a061b2c24a</wwpn>
<==== all numbers are random, as expected

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2019:0521