Unable to start a guest using qemu-kvm directly

Unable to start a guest using qemu-kvm directly

[Vinod Chegu]

Dear All,

I am using RHEL 6.2 + KVM on a X86_64 server.  I have been able to create Linux 
guests using virt-install (using virto and/or pci passthrough) and am able to 
manage the guests using virsh and/or virt-manager for doing some basic stuff. 

Here is a sample guest (that I was able to create using virt-install and able to 
boot fine using either virsh or virt-manager) :


<domain type='kvm' id='11'>
  <name>testvm2</name>
  <uuid>d44e8618-e48c-531b-01c4-80fc2a026a25</uuid>
  <memory>4194304</memory>
  <currentMemory>4194304</currentMemory>
  <vcpu>1</vcpu>
  <os>
    <type arch='x86_64' machine='rhel6.2.0'>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'>
      <driver name='qemu' type='qcow2' cache='none'/>
      <source file='/var/lib/libvirt/images/vmStorage/vm2.img'/>
      <target dev='vda' bus='virtio'/>
      <alias name='virtio-disk0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' 
function='0x0'/>
    </disk>
    <disk type='block' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <target dev='hdc' bus='ide'/>
      <readonly/>
      <alias name='ide0-1-0'/>
      <address type='drive' controller='0' bus='1' unit='0'/>
    </disk>
    <controller type='ide' index='0'>
      <alias name='ide0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' 
function='0x1'/>
    </controller>
    <interface type='bridge'>
      <mac address='52:54:00:7b:dc:d3'/>
      <source bridge='vbr1'/>
      <target dev='vnet0'/>
      <model type='virtio'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' 
function='0x0'/>
    </interface>
    <serial type='pty'>
      <source path='/dev/pts/4'/>
      <target port='0'/>
      <alias name='serial0'/>
    </serial>
    <console type='pty' tty='/dev/pts/4'>
      <source path='/dev/pts/4'/>
      <target type='serial' port='0'/>
      <alias name='serial0'/>
    </console>
    <input type='tablet' bus='usb'>
      <alias name='input0'/>
    </input>
    <input type='mouse' bus='ps2'/>
    <graphics type='vnc' port='5900' autoport='yes'/>
    <video>
      <model type='cirrus' vram='9216' heads='1'/>
      <alias name='video0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' 
function='0x0'/>
    </video>
    <memballoon model='virtio'>
      <alias name='balloon0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' 
function='0x0'/>
    </memballoon>
  </devices>
  <seclabel type='dynamic' model='selinux' relabel='yes'>
    <label>system_u:system_r:svirt_t:s0:c290,c578</label>
    <imagelabel>system_u:object_r:svirt_image_t:s0:c290,c578</imagelabel>
  </seclabel>
</domain>

 

Tried to start the above guest using qemu-kvm directly (so that I can in future 
specify different options etc).  But I am getting some errors. (pl. see below).

# /usr/libexec/qemu-kvm -version
QEMU PC emulator version 0.12.1 (qemu-kvm-0.12.1.2), Copyright (c) 2003-2008 
Fabrice Bellard

# /usr/libexec/qemu-kvm -S -M rhel6.2.0 -enable-kvm -m 4096 -smp 
1,sockets=1,cores=1,threads=1 -name testvm2 -uuid d44e8618-e48c-531b-01c4-
80fc2a026a25 -nodefconfig -nodefaults -chardev 
socket,id=charmonitor,path=/var/lib/libvirt/qemu/testvm2.monitor,server,nowait -
mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -no-shutdown -
drive file=/var/lib/libvirt/images/vmStorage/vm2.img,if=none,id=drive-virtio-
disk0,format=qcow2,cache=none -device virtio-blk-
pci,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -
drive if=none,media=cdrom,id=drive-ide0-1-0,readonly=on,format=raw -device ide-
drive,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 -netdev 
tap,fd=23,id=hostnet0,vhost=on,vhostfd=24 -device virtio-net-
pci,netdev=hostnet0,id=net0,mac=52:54:00:7b:dc:d3,bus=pci.0,addr=0x3 -chardev 
pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -usb -
device usb-tablet,id=input0 -vnc 127.0.0.1:0 -vga cirrus -device virtio-balloon-
pci,id=balloon0,bus=pci.0,addr=0x5


char device redirected to /dev/pts/5
qemu-system-x86_64: -netdev tap,fd=23,id=hostnet0,vhost=on,vhostfd=24: TUNGETIFF 
ioctl() failed: Bad file descriptor
TUNSETOFFLOAD ioctl() failed: Bad file descriptor
qemu-system-x86_64: -netdev tap,fd=23,id=hostnet0,vhost=on,vhostfd=24: vhost-net 
requested but could not be initialized
qemu-system-x86_64: -netdev tap,fd=23,id=hostnet0,vhost=on,vhostfd=24: Device 
'tap' could not be initialized



----
Can someone please tell me what this means and any tips on how I can solve this? 
Do I have to do some other setup to make qemu-kvm happy w.r.t the -netdev 
options?


Thank you in anticiaption!!
Vinod

Re: Unable to start a guest using qemu-kvm directly

[Michael Tokarev]

On 29.01.2012 19:17, Vinod Chegu wrote:
> 
> Dear All,
> 
> I am using RHEL 6.2 + KVM on a X86_64 server.  I have been able to create Linux 
> guests using virt-install (using virto and/or pci passthrough) and am able to 
> manage the guests using virsh and/or virt-manager for doing some basic stuff. 
> 
> Here is a sample guest (that I was able to create using virt-install and able to 
> boot fine using either virsh or virt-manager) :
> 
[]
> Tried to start the above guest using qemu-kvm directly (so that I can in future 
> specify different options etc).  But I am getting some errors. (pl. see below).
> 
> # /usr/libexec/qemu-kvm -version
> QEMU PC emulator version 0.12.1 (qemu-kvm-0.12.1.2), Copyright (c) 2003-2008 
> Fabrice Bellard
> 
> # /usr/libexec/qemu-kvm -S -M rhel6.2.0 -enable-kvm -m 4096 -smp 
> 1,sockets=1,cores=1,threads=1 -name testvm2 -uuid d44e8618-e48c-531b-01c4-
> 80fc2a026a25 -nodefconfig -nodefaults -chardev 
> socket,id=charmonitor,path=/var/lib/libvirt/qemu/testvm2.monitor,server,nowait -
> mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -no-shutdown -
> drive file=/var/lib/libvirt/images/vmStorage/vm2.img,if=none,id=drive-virtio-
> disk0,format=qcow2,cache=none -device virtio-blk-
> pci,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -
> drive if=none,media=cdrom,id=drive-ide0-1-0,readonly=on,format=raw -device ide-
> drive,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 -netdev 
> tap,fd=23,id=hostnet0,vhost=on,vhostfd=24 -device virtio-net-
      ^^^^^                      ^^^^^^^^^^
> pci,netdev=hostnet0,id=net0,mac=52:54:00:7b:dc:d3,bus=pci.0,addr=0x3 -chardev 
> pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -usb -
> device usb-tablet,id=input0 -vnc 127.0.0.1:0 -vga cirrus -device virtio-balloon-
> pci,id=balloon0,bus=pci.0,addr=0x5
> 
> 
> char device redirected to /dev/pts/5
> qemu-system-x86_64: -netdev tap,fd=23,id=hostnet0,vhost=on,vhostfd=24: TUNGETIFF 
> ioctl() failed: Bad file descriptor

libvirt pre-configures network tap devices and pre-opens
/dev/vhost-net file and passes these to qemu[-kvm] as
open, ready to use file descriptors.  Like you can do
to redirect stdin:

 cat file

there, cat opens "file" and reads it, or

 cat < file

where cat reads stdin.

In particular, libvirtd has more privileges to open
tap and vhost-net devices since it does that as root
but spawns qemu[-kvm] as unprivileged user.

[]
> Can someone please tell me what this means and any tips on how I can solve this? 
> Do I have to do some other setup to make qemu-kvm happy w.r.t the -netdev 
> options?

You need to understand how to (pre-)configure networking
for qemu (pre- if you want to run it as non-root), this
is described in the users guide and in a lot of howtos
all around the 'net.

/mjt

Re: Unable to start a guest using qemu-kvm directly

[Vinod Chegu]

Michael Tokarev <mjt <at> tls.msk.ru> writes:

> 
> You need to understand how to (pre-)configure networking
> for qemu (pre- if you want to run it as non-root), this
> is described in the users guide and in a lot of howtos
> all around the 'net.
> 
> /mjt


Thanks! I was able to find the needed info to bring the guest up and connect
to it etc.

Vinod