Re: [Xen-users] Serial Passthrough broken in Debian Wheezy?

[Jonas Meurer <jonas@xxxxxxxxxxxxxxx>]

Hey,

Am 2013-06-03 18:17, schrieb Ian Campbell:
> On Mon, 2013-06-03 at 17:25 +0200, Jonas Meurer wrote:
> > Hello,
> >
> > did anybody else discover issue with serial passthrough on Linux 3.2.0
> > from Debbian Wheezy?
> I haven't, but Squeeze was based on the out of tree xen.git kernel 
> while
> Wheezy uses the mainline pvops support, so this is probably an issue
> with the mainline kernel. I can't quite imagine what it would be 
> though.
> Are you able to try an newer upstream kernel in your domU? Either a
> newer version from Debian Sid or wheezy-backports or a self compiled
> one.
Just gave Linux 3.9-1-amd64 from Debian/sid a try. The issue is 
reproducible with this DomU kernel.
Kind regards,
 jonas

> > Am 2013-05-14 14:56, schrieb Jonas Meurer:
> > > Hey again,
> > >
> > > Am 13.05.2013 17:58, schrieb Jonas Meurer:
> > >> I just discovered a strange bug with serial passthrough in xen 4.1 on
> > >> Debian Wheezy. The Dom0 has a GSM modem connected to serial port. The
> > >> serial port is passed through to a DomU with options 'irq = [ 4 ]' and
> > >> 'ioports = [ '3f8-3ff ]'.
> > >
> > > While searching the list archives I found out, that latest Xen 4.1 has
> > > several issues with passthrough. But so far it seems to me like nobody
> > > else described my exact issue before. Apparently, the other passthrough
> > > issues have been introduced by a hypervisor update. My problem appeared
> > > after a kernel upgrade. And for me, DomU creation still works. As
> > > described, the passed through serial even exists in DomU. Only it
> > > doesn't behave as expected.
> > >
> > > Just wanted to share those additional observations.
> > >
> > > Kind regards,
> > >  jonas
> > >
> > >>
> > >> This worked as expected on Debian Squeeze with Xen 4.0 and Linux
> > >> kernel
> > >> 2.6.32 (both for Dom0 and DomU). On Debian Wheezy with Xen 4.1 and
> > >> Linux kernel 3.2.0 the passthrough seems to work as well (/dev/ttyS0
> > >> appears in dmesg of DomU), but something is wrong. The GSM modem
> > >> doesn't behave as expected. The smstools daemon errors out with
> > >> 'Cannot
> > >> open serial port /dev/ttyS0, error: Function not implemented'.
> > >>
> > >> It took me hours to find the difference, but it seems like the guest
> > >> (domU) kernel is the problem. The setup keeps working when Dom0 is
> > >> upgraded to Debian Wheezy with Xen 4.1 and linux kernel 3.2.0. It even
> > >> keeps working if the DomU userland is upgraded to Debian Wheezy. Only
> > >> if I upgrade the DomU linux kernel to 3.2.0 from Wheezy as well,
> > >> smstools stops working.
> > >>
> > >> I don't expect this to be a smstools bug. More likely, something
> > >> regarding serial pass through functions of xen is broken in 3.2.0
> > >> kernel from Debian Wheezy.
> > >>
> > >> Did anybody else discover similar issues yet?
> > >>
> > >> Kind regards,
> > >>  jonas
> > >>
> > >> PS: I'm not subscribed to pkg-xen-devel@xxxxxxxxxxxxxxxxxxxxxxx,
> > >> please
> > >> cc me on that list.

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