Re: Problems with serial interrupts with IPMI 2.0 SoL

Mauro Carvalho Chehab
2009-12-10T23:56:04Z

Em Thu, 10 Dec 2009 13:45:54 -0800
Jeremy Fitzhardinge <jeremy@goop.org> escreveu:

> Hi,
>
> I'm using a system with an embedded IPMI 2.0 BMC which provides SoL
> (Supermicro X8SIL-F). This works fine under Linux (fully interrupt
> driven), but fails for Xen as it appears to not be sending interrupts;
> it works OK if I set the driver to polling mode.
>
> I'm assuming the Xen is tickling some bug in the emulated 16550. The
> Linux driver has a couple of pieces of code to explicitly work around
> bugs in the Intel AMT SoL implementation, but I don't think they're
> coming into play here (because there are no Intel SoL PCI devices on
> this system to trigger the NO_TXEN_TEST flag).
>
> I'm wondering if you have any pointers or suggestions about more subtle
> problems?

If you don't hit NO_TXEN_TEST flag, you'll be loosing interrupts, as the
emulation of 16550 is not perfect.

As far as I remember, interrupts take too long to happen with the emulated
16550, when comparing with a normal serial.

--

Cheers,
Mauro