Messages in this thread | | | Date | Thu, 7 Feb 2008 13:39:38 +0100 | From | Ingo Molnar <> | Subject | Re: 2.6.24 says "serial8250: too much work for irq4" a lot. |
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* H. Peter Anvin <hpa@zytor.com> wrote:
>> (If it's a qemu issue, I can go bother them. It's possible that qemu >> isn't delivering interrupts as often as it expects, since that's >> limited by the granularity of the host timer; I know the clock in >> qemu can run a bit slow because it only gets clock interrupts when >> the host system isn't too busy to schedule the emulator. But this >> doesn't usually cause a problem. I _think_ the message is just a >> "this should never happen" type warning, which is happening to me. >> But I break stuff. :) > > This is because Qemu spews data to the serial port without any rate > limiting; this causes the in-kernel serial port driver to think the > port is stuck. The serial port emulation needs to make it possible to > drain the virtual FIFO every now and then, as opposed to filling it > again immediately.
actually, the way i solved it for qemu+KVM+paravirt was to just turn off this rather silly check in the serial driver if inside a paravirt guest. When we are emulated then the serial 'hardware' is totally reliable and we should just trust it. That way i never dropped a single bit of kernel log output again.
Ingo
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