Bug#428895: No way to use serial console with Xen kernel

[Dave Pifke <dave@birthdayalarm.com>]

Package: linux-image-2.6.18-4-xen-amd64
Version: 2.6.18.dfsg.1-12etch2

It appears that the 2.6.18-4 kernel in Etch does not support 8250 serial 
devices.  I see the following messages in dmesg when I boot up:

Serial: 8250/16550 driver $Revision: 1.90 $ 4 ports, IRQ sharing enabled
8250_pnp: Unknown symbol serial8250_unregister_port
8250_pnp: Unknown symbol serial8250_register_port
Serial: 8250/16550 driver $Revision: 1.90 $ 4 ports, IRQ sharing enabled
8250_pnp: Unknown symbol serial8250_unregister_port
8250_pnp: Unknown symbol serial8250_register_port

The devices are enabled in the BIOS and work correctly when running the 
stock 2.6.18-4 kernel.  When booting with that version, the relevant 
dmesg lines look like:

Serial: 8250/16550 driver $Revision: 1.90 $ 4 ports, IRQ sharing enabled
serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
serial8250: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A

This appears to be a Xen issue, since Xen steals the ttyS* devices for 
xencons.  I found a reference to a possible fix here:

http://www.nabble.com/xen-console-question-t690692.html

As the server is at a remote data center with RS232 console being the 
only available way to access it in the event of network problems, I'd 
like to see the 8250/16550 driver re-enabled in the Xen kernel.