Re: Serial Port Driver does not handle interrupt

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

Erik Rull wrote:
> 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
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fixed, apic on host side was disabled, kvm / qemu seems to need it.