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Description of problem:
I have two virtual QEMU/KVM virtual machines on a Fedora 7 x86_64 machine.
Both are running "hardware-accelerated ?" (QEMU + KVM). The 'virbr0'
virtual network is started by default by libvirtd et. al. (?) on
I can run both machines separately, i.e., one at a time, but cannot
run both together. Whenever trying to start the second virtual
machine I get a particular error which I'll describe later.
One virtual machine is Fedora Core 7 running x86_64 (QEMU + KVM).
The other virtual machine is Windows XP Pro SP 2 (SP 2 from install,
not applied post-install), running on i686 (QEMU + KVM, I'm supposing
hardware KVM works on x86_64 for i686 since the virtual machine runs
fine in i686 other than this networking issue).
Version-Release number of selected component (if applicable):
qemu-0.9.0-2.fc7 libvirt-0.2.3-1.fc7 kvm-24-1 (libvirt-python-0.2.3-1.fc7 ??)
Steps to Reproduce:
 Boot machine into *.fc7 (not *.fc7xen) kernel, along with
'qemu' and 'libvirtd' daemons started at beginning
 virtual network 'virbr0' started automatically, config file
 start either virtual machine 'BogatzaFedora7M01' or
'BogatzaWinXpProM02', both are configured to attach to
'virbr0' (this step succeeds) -- NOTE: I used virt-manager
to create/install both virtual machines, and also to
start/stop the virtual machines
 while first virtual machine is one, try to start the
other virtual machine, which also attaches to 'virbr0'
virtual network (start from virt-manager) --
THIS STEP FAILS WITH ERROR SHOW IN THE "Actual Results"
In every case where I try to start second virtual machine I get
a virt-manager error dialog box exposing an error seen at the Python
level (must be virt-manager impl lang?). The dialog box has as
virDomainCreate() failed internal error Failed to add tap
interface 'vnet0' to bridge 'virbr0': Device or resource busy
... there is a Details "button" allowing one to see more error
details, the details read:
Unable to start virtual machine '<class 'libvirt.libvirtError'> virDomainCreate() failed internal error Failed to add tap interface 'vnet0' to bridge
'virbr0' : Device or resource busy
Traceback (most recent call last):
File "/usr/share/virt-manager/virtManager/console.py", line 348, in control_vm_run
File "/usr/share/virt-manager/virtManager/domain.py", line 361, in startup
File "/usr/lib64/python2.5/site-packages/libvirt.py", line 217, in create
if ret == -1: raise libvirtError ('virDomainCreate() failed', dom=self)
libvirtError: virDomainCreate() failed internal error Failed to add tap interface 'vnet0' to bridge 'virbr0' : Device or resource busy
There is no workaround that I can see since it's necessary and
essential to attach multiple machines to the same virtual
virt-manager/libvirt, etc., should start second virtual machine without
complaining and without problem.
(And I assume the 'veth0' is a virtual-machine-visible interface
name, and that the 'veth0' apparently started by the two machines
should not conflict in namespace with each other. In any case,
I'll probably try to state an explicit 'veth1' for the Windows XP
virtual machine definition, because (a) it's missing; and (b) it
might resolve the problem by avoiding namespace/perceived-device
(I might also try creating a second virtual network 'virbr1' and
attaching the two machines to independent networks or to the
second network and see what happens there.)
--- DIRECTORY LISTING FOR: /etc/libvirt/qemu (config dir for QEMU virt env)
--- config for Fedora 7 virt machine, untouched/unedited, as created/maintained
<disk type='block' device='disk'>
<graphics type='vnc' port='-1'/>
--- config for in XP virt machine, untouched/unedited, as created/maintained
<disk type='block' device='disk'>
<graphics type='vnc' port='-1'/>
--- config for 'default' network 'virbr0', edited only to change the
DHCP range (and the problem occurred before ever changing this
DHCP range by hand and re-booting)
<bridge name="virbr0" />
<ip address="192.168.122.1" netmask="255.255.255.0">
<range start="192.168.122.100" end="192.168.122.110" />
One more thing: whenever I run into the problem starting
the second virtual machine, if I shut down the first virtual
machine and then try again to start the "second" virtual
machine, it succeeds.
OK ... the thing where I add an explicit 'veth1' to the
Windows XP thing seems to work OK ... haven't tried the
networking in the Windows XP virtual machine (i.e., I'm
not sure the Win XP machine will actually find the new
virtual interface), but at least both machines start up.
... with some more work ... I find that both virtual
machines now can start up together, and that they both
can 'ping' internal and external targets, and internet
browsers can reach and pull down www.yahoo.com.
Based on this I'm changing the bug title from: "Running 2nd
QEMU/KVM virtual machine fails when setting up virtual
networking to bridge 'virbr0'" to "virt-manager/libvirt
creates Windows XP virtual machine with no explicit
'vethX' interface name leading to conflict with
'veth0' in other virtual machine" -- I believe that's what happened.
I suppose the 'vethX' stuff can conflict namespace-wise at
the host level and must be unique across all virtual machines (?).
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