Re: [Xen-users] Serial port in domU

[Ernst Bachmann <e.bachmann@xxxxxxxx>]

On Wednesday 27 July 2005 15:58, Giovanni Bordello wrote:

>
> How much work would it be to assign the port to domU?

Well, Serial Ports (16550 & co) still are accessed like ISA bus devices, for 
compatibility with DOS & PC/XT. Xen AFAIK only has support for giving PCI 
devices to domains other than domU, and I highly doubt that anyone is willing 
to implement ISA device sharing. So the easy solution of giving the serial 
port hardware to domU is IMHO out of the question (unless you have a 
PCI->Serial card, but then it should already work with the existing PCI 
sharing code)

So what would be needed is a "Virtual character device", working like the 
Blockdevice FE/BE drivers, but transfering the ttyS device (with all IOCTLs 
and whatnot) to domU. (Quite a security hole, considering what you can do 
with IOCTLs on serial devices, but I'd guess its ok for trusted domUs)

I think the much easier solution in your case would be to split your message 
server thingy in half, keeping a backend with HW access in dom0, and the 
application logic in domU, and only transfer the messages it should send over 
TCP.

/Ernst

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