Serial Port Driver does not handle interrupt

[Erik Rull <erik.rull@rdsoftware.de>]

Hi all,

I've tested two kvm versions 77 and 88, both with the same behaviour:
I add a serial device with -serial /dev/ttyS0 to my guest and launched 
HyperTerm on my Windows Guest.
Additionally I plugged in a loopback plug on the serial connector that just 
routes back the data send back to the receive line (TXD -> RXD).
When I enter characters on the Hyperterm all characters are displayed 
except the last one that was sent.
When I plug in a real serial device and request its status via Hyperterm I 
get only back the first 16 chars (I expect 50) when I send an additional 
dummy character (sizeof: 16550 FIFO buffer). On my normal Windows PC it 
works as expected - so it seems to be an issue with kvm.

In the linux host, I don't see any changes in /proc/interrupts, the driver 
is opened and exclusively on this interrupt line.

Within the host the serial line works without any problems, and there, the 
interrupt counts increase during normal operation with a software that runs 
on the host and that uses this serial line.

What must I do to bring the serial line to real life with a complete 
communication without any data lost caused by missing interrupts? At the 
moment this is a key issue that has to be solved to continue my work with kvm.

Any Ideas? I also tested other IRQ lines and other ttyS* on the system - 
same behaviour.

Thanks in advance,

Erik