kvm中已编译内核中缺少通道

Question

I have a ubuntu in virtual machine using libvirt. I configured my guest to create pipe and unix channels for trace-virtio purpose:

<channel type='unix'>
  <source mode='connect' path='path/to/socket'/>
  <target type='virtio' name='unix-name'/>
  <address type='virtio-serial' controller='0' bus='0' port='1'/>
</channel>
<channel type='pipe'>
  <source path='path/to/pipe'/>
  <target type='virtio' name='pipe-name'/>
  <address type='virtio-serial' controller='0' bus='0' port='2'/>
</channel>

Everything works fine in my guest and I have my channel in /dev inside my virtual machine and I can send data to host using these channels. But when I compile kernel and install it inside my vm and select it from grub, these channels disappear. When I reboot and select the original kernel, it has the channels and works correctly. How can I tell kvm to create channels in compiled kernel inside my virtual machine?

Answer 1

Ensure that the kernel you are building for your guests has the same config options as the one that worked.

You can get these from /proc/kconfig (if you are lucky and the kernel has that compiled in) else from a config distributed with the kernel (normally in the /boot directory.

The relevant ones are likely to be the guest kvm options described here . In particular, ensure the VIRTIO options are on. My guess is you are missing VIRTIO_CONSOLE (which is in fact character devices).