Xen devel - Dec 2009 - Problems with serial interrupts with IPMI 2.0 SoL

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?

Thanks,
     J

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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

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