Bug 510179

Description of problem:
when element "dev"'s value is "xvda",element "bus" will be assigned "xen",if user input dev="xvda" in guest configure file on kvm host,error configure will be generated and defined

Version-Release number of selected component (if applicable):
[root@dhcp-66-70-18 libvirt]# uname -a
Linux dhcp-66-70-18.nay.redhat.com 2.6.18-153.el5 #1 SMP Wed Jun 10 17:53:33 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux
[root@dhcp-66-70-18 libvirt]# lsmod|grep kvm
kvm_intel              85992  0 
kvm                   222368  2 ksm,kvm_intel
[root@dhcp-66-70-18 libvirt]# rpm -qa|grep kvm
kvm-qemu-img-83-76.el5
kvm-83-84.el5
etherboot-zroms-kvm-5.4.4-10.el5
kmod-kvm-83-76.el5
[root@dhcp-66-70-18 libvirt]# rpm -qa|grep libvirt
libvirt-cim-0.5.5-2.el5
libvirt-0.6.3-14.el5
libvirt-python-0.6.3-14.el5
libvirt-debuginfo-0.6.3-14.el5
libvirt-devel-0.6.3-14.el5

How reproducible:
100%

Steps to Reproduce:
1.create a guest xml on kvm host
2.virsh define kvm.xml
or
[root@dhcp-66-70-18 libvirt]# python
Python 2.4.3 (#1, Sep 17 2008, 16:07:08) 
[GCC 4.1.2 20071124 (Red Hat 4.1.2-41)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import libvirt
>>> conn=libvirt.open(None)
>>> fp=open("kvm.xml","r")
>>> xml_desc=fp.read()
>>> print xml_desc
<?xml version='1.0' encoding='UTF-8'?>
<domain type='kvm'>
  <name>RHEL5.3-Server_http.qcow2</name>
  <uuid>af70873a-3e15-4e6b-bfa4-143f303d1941</uuid>
  <memory>1048576</memory>
  <vcpu>1</vcpu>
  <os>
    <type arch='x86_64'>hvm</type>
  </os>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>
  <features>
    <acpi/>
    <apic/>
    <pae/>
  </features>
  <devices>
    <emulator>/usr/libexec/qemu-kvm</emulator>
    <disk device='disk' type='file'>
      <source file='/var/lib/libvirt/images/RHEL5.3-Server_http.qcow2'/>
      <target dev='xvda'/>
    </disk>
    <interface type='network'>
      <mac address='80:a6:9c:6e:b3:6d'/>
      <source network='virbr0'/>
    </interface>
    <input bus='ps2' type='mouse'/>
    <graphics keymap='en-us' type='vnc' port='-1'/>
    <console/>
  </devices>
</domain>

>>> dom=conn.defineXML(xml_desc)
>>> print dom.XMLDesc(0)
<domain type='kvm'>
  <name>RHEL5.3-Server_http.qcow2</name>
  <uuid>af70873a-3e15-4e6b-bfa4-143f303d1941</uuid>
  <memory>1048576</memory>
  <currentMemory>1048576</currentMemory>
  <vcpu>1</vcpu>
  <os>
    <type arch='x86_64' machine='pc'>hvm</type>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <pae/>
  </features>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>
  <devices>
    <emulator>/usr/libexec/qemu-kvm</emulator>
    <disk type='file' device='disk'>
      <source file='/var/lib/libvirt/images/RHEL5.3-Server_http.qcow2'/>
      <target dev='xvda' bus='xen'/>
    </disk>
    <interface type='network'>
      <mac address='80:a6:9c:6e:b3:6d'/>
      <source network='virbr0'/>
    </interface>
    <serial type='pty'>
      <target port='0'/>
    </serial>
    <console type='pty'>
      <target port='0'/>
    </console>
    <input type='mouse' bus='ps2'/>
    <graphics type='vnc' port='-1' autoport='yes' keymap='en-us'/>
  </devices>
</domain>

  
Actual results:
a guest with the wrong config was defined.

Expected results:
The guest with wrong xml config should not be defined successfully.

Additional info: