Re: [Xen-devel] serial ports in a pv domU

[Michael D Labriola <mlabriol@xxxxxxxx>]

xen-devel-bounces@xxxxxxxxxxxxxxxxxxx wrote on 03/19/2010 03:36:57 PM:

> xen-devel-bounces@xxxxxxxxxxxxxxxxxxx wrote on 03/19/2010 01:29:22 PM:
> 
> > On Fri, 2010-03-19 at 17:21 +0000, Michael D Labriola wrote:
> > > Is there a way to pass a system's on-board serial port(s) into a 
> > > paravirtualized domU?
> > 
> > I think you can pass individual IO ports and interrupt through to a PV
> > guest without necessarily passing through a PCI device. 
> > 
> > I'm afraid I don't actually know the exact runes to cause xend or xl 
or
> > whatever to do this though -- I think perhaps for xend lines like:
> >    ioport=03f8-03f9
> >    irq=3
> > (or whatever the com port uses) in your config file might do the 
trick.
> > 
> > > I don't have any on hand to test with, but would passing a PCI 
serial 
> card 
> > > into the domU have any issues?
> > 
> > I'd expect that to work alright.
> 
> Hmm, thought I had this working.  With 'ioports = ['3f8-3ff']' and 
> 'irq=[4]' in my cfg file, I get appropriate messages in domU's dmesg 
about 
> initializing ttyS0...  But the device doesn't seem to work.  And the 
> device still works in dom0...
> 
> I looked at the old InstallationNotes Wiki (last touched Nov 2007?) 
which 
> says to blacklist the 8250, 8250_pnp, and serial_core modules... is this 

> still needed with the pv_ops kernels?  Pretty sure I've got the serial 
> stuff compiled into the kernel, so I can't really blacklist those unless 
I 
> recompile.  I tried unbinding the devices from their driver via sysfs, 
but 
> then the devices don't show up in domU at all...

Odd... after breaking everything by manually unbinding from the serial 
driver, I rebooted.  And now my domU has ttyS0 and it actually works.

---
Michael D Labriola
Electric Boat
mlabriol@xxxxxxxx
401-848-8871 (desk)
401-848-8513 (lab)
401-316-9844 (cell)



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