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


Am 2013-06-03 18:17, schrieb Ian Campbell:
On Mon, 2013-06-03 at 17:25 +0200, Jonas Meurer wrote:

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

Just gave Linux 3.9-1-amd64 from Debian/sid a try. The issue is reproducible with this DomU kernel.

Kind regards,

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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