Re: [Qemu-devel] [PATCH 10/13] Implement early printk in virtio-console

[Alexander Graf]

On 24.11.2009, at 20:25, Anthony Liguori wrote:

> Alexander Graf wrote:
>> On 24.11.2009, at 19:55, Anthony Liguori wrote:
>> 
>>  
>>> Alexander Graf wrote:
>>>    
>>>> On our S390x Virtio machine we don't have anywhere to display early printks
>>>> on, because we don't know about VGA or serial ports.
>>>> 
>>>> So instead we just forward everything to the virtio console that we created
>>>> anyways.
>>>>       
>>> What is this used for?
>>>    
>> 
>> This is used for console output before virtio is initialized. I didn't 
>> invent it - that's the way it's implemented in the s390 kernels today.
>>  
> 
> I don't see any code that calls this function.  Am I missing something 
> obvious?

It gets called from target-s390x/kvm.c using a special hypercall instruction.

Alex