[Pkg-xen-devel] [Xen-users] Serial Passthrough broken in Debian Wheezy?

[Jonas Meurer]

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 at lists.alioth.debian.org,
>> >> please
>> >> cc me on that list.