[libvirt] Fwd: Re: need your help about virito vmchannel

[Cole Robinson]

On 05/04/2010 12:38 PM, Matthew Booth wrote:
> FYI for the list. I haven't looked at this yet.
> 
> Matt
> 
> -------- Original Message --------
> Subject: Re: need your help about virito vmchannel
> Date: Tue, 4 May 2010 18:00:02 +0530
> From: Amit Shah <amit.shah at redhat.com>
> To: Matthew Booth <mbooth at redhat.com>
> CC: Jianlin Liu <jialiu at redhat.com>
> 
> On (Tue) May 04 2010 [13:18:30], Matthew Booth wrote:
>> On 04/05/10 12:48, Jianlin Liu wrote:
>>> Hi Matthew,
>>>
>>>    I want to create a virtio vm channel in my guest. So I add the followiong to my guest xml file:
>>> <channel type='pty'>
>>>   <target type='virtio' name='org.linux-kvm.port.0'/>
>>> </channel>
>>
>> Jianlin,
>>
>> While I wrote the libvirt->vmchannel glue, I'm not actually that
>> familiar with vmchannel itself. I've cc'd Amit, who hopefully might
>> recognise this problem and tell me how to fix it ;)
>>
>> Amit,
>>
>> Any idea what's going on here?
> 
> Yes:
> 
>>> Then I try to start the guest:
>>> # virsh start winxp
>>> error: Failed to start domain winxp
>>> error: internal error Process exited while reading console log output: char device redirected to /dev/pts/4
>>> char device redirected to /dev/pts/5
>>> qemu-kvm: -device virtio-serial-pci,id=virtio-serial0,max_ports=0,vectors=0,bus=pci.0,addr=0x5: Device 'virtio-serial-pci' could not be initialized
> 
> With max_ports=0, the virtio-serial device doesn't get created and hence
> this error.
> 
> 		Amit
> 

I saw this issue as well, when I started adding channel support to
virt-install (since stalled, but mostly complete). Adding a <channel>
device creates an implicit virtio-serial controller which defaults to
ports = 0.

Since ports = 0 is useless, maybe we should just defer to the qemu
default for that case (which is 31 according to
http://fedoraproject.org/wiki/Features/VirtioSerial ). We should
probably find a way to do the same thing for the 'vectors' value as
well, although 0 is valid value there.

- Cole