Re: [Qemu-devel] [PATCH 3/4] virtio-console: Add support for multiple ports for generic guest-host communication

[Amit Shah]

On (Wed) Sep 23 2009 [15:04:27], Gerd Hoffmann wrote:
>>> -device virtio-console
>>>     Creates the portbus master.  No ports (yet).
>>>
>>> -device vmport-console,chardev=$dev
>>>     Creates a port named 'org.qemu.console' and links it to $dev.
>>
>> OK; that's what I have now, slightly different:
>>
>> -device virtio-console-pci -device virtconport,port=0,chardev=$dev
>
> Fine as well.  The exact names don't really matter, the naming for the  
> port drivers should be consistent though (i.e. have the same prefix for  

Yes.

> all of them or something like that).  Optional port number looks  
> reasonable too.  Should default to auto-allocation if not specified.

Once that gets decided :-)

It's still not decided if we'll be optional port numbers vs assigned.

>>> For backward-compatibility we'll allways have to create a vmport-console
>>> at port 0, so there will never be a virtio-console without a port.  That
>>> is a minor bit we can fixup once the above works fine.
>>
>> ie -virtioconsole<chardev>  ?
>
> There are two kinds of backward compatibility ;)  One is the qemu  

Yes, I wanted to know which one you're thinking about.

> command line.  The other is the ABI for old guest drivers.  The later  
> requires a console at port 0 ...

For that, there are two options:

1. If we go with a static port function -> port number mapping, this is
easy (as I already have now).
2. If we go with dynamic numbers, the guest could register the hvc
console only for a device that has the name 'org.qemu.console.0'. This
supports multiple ports as well.

>> I'd suggest we just drop that in 0.12.
>
> Dropping the command line switch is with me.  In case someone disagrees  
> (libvirt folks?) it isn't hard to maintain compatibility though.

It's not much effort to maintain that, but the old and new syntaxes are
very different. qemu 0.11 doesn't offer the ability to support multiple
virtioconsoles, but 0.12 will. So the cmd line syntax has to change for
that anyway, might as well deprecate the older syntax.

                Amit