Bug#766607: linux: ("regression") No serial console output when connecting to virtual serial console for the guest during d-i installation initiated via virt-install

[Salvatore Bonaccorso <carnil@debian.org>]

Source: linux
Version: 3.16~rc5-1~exp1
Severity: important

Hi Ben

I choosed important as severity, as it causes a regression from
wheezy->jessie for installation of kvm guests with kernel in the d-i,
but actually it might be overrated, please downgrade if you don't
agree.

Background: For tests I often use the following instruction to quickly
create vms (either preseeded or without preseed):

http://honk.sigxcpu.org/con/Preseeding_Debian_virtual_machines_with_virt_install.html

also having the console output to ttyS0, the kernel arguments are 

auto keymap=us hostname=foo netcfg/get_ipaddress=192.168.122.123 suite=unstable -- console=ttyS0,115200n8

in the example case.

When altough using the current d-i with a 3.16.2-2 the kernel I don't
see anymore neither the kernel boot messages nor the started d-i
anymore when virt-install connects to the virtual serial console for
the guest and cannot proceed with installation in d-i.

I was able to track this down to a change between 3.15.5-1~exp1 and
3.16~rc5-1~exp1 but unfortuantely don't have a specific commit.

To reproduce I attach the small 'reproducer.sh' shellscript which
fetches the d-i linux and initrd.gz from
-location=${HOME}/virt/installer-amd64/ (see below) and also sets 

auto keymap=us hostname=foo netcfg/get_ipaddress=192.168.122.123 suite=unstable -- console=ttyS0,115200n8

as kernel arguments. It is

----cut---------cut---------cut---------cut---------cut---------cut-----
#!/bin/bash

virt-install --connect=qemu:///system \
        --graphics none \
	--location=${HOME}/virt/installer-amd64/ \
	--extra-args="auto keymap=us hostname=foo netcfg/get_ipaddress=192.168.122.123 suite=unstable -- console=ttyS0,115200n8" \
	--name foo \
	--ram 1024 \
	--disk=pool=default,size=5,format=qcow2,bus=virtio,cache=writeback
----cut---------cut---------cut---------cut---------cut---------cut-----

${HOME}/virt/installer-amd64 would look as follows:

----cut---------cut---------cut---------cut---------cut---------cut-----
$ ls -1R installer-amd64
installer-amd64:
current

installer-amd64/current:
images

installer-amd64/current/images:
MANIFEST
netboot

installer-amd64/current/images/netboot:
debian-installer

installer-amd64/current/images/netboot/debian-installer:
amd64

installer-amd64/current/images/netboot/debian-installer/amd64:
initrd.gz
linux
----cut---------cut---------cut---------cut---------cut---------cut-----

and the MANIFEST file only need to contain

----cut---------cut---------cut---------cut---------cut---------cut-----
netboot/debian-installer        -- PXE boot directory for tftp server
----cut---------cut---------cut---------cut---------cut---------cut-----

So basically stripped down content as you would find in
http://ftp.ch.debian.org/debian/dists/unstable/main/installer-amd64/

If I use initrd.gz and linux from 20140802 installation works fine if
I use the ones from current (20141002) the above behavious is
observed, no installer ist seen.

I then afterwards replaced the linux image to find closer version were
the problem appear, and looks like 3.15.5-1~exp1 is good,
3.16~rc5-1~exp1 is bad. Quite some changes with merge in commit
49eb7b0750d9483c74e9c14ae6ea1e9d62481c3c

The mentioned setup is running on Debian stable with
libvirt/0.9.12.3-1+deb7u1, qemu-kvm/1.1.2+dfsg-6+deb7u4.

Regards,
Salvatore