Comment 35 for bug 1879987

Verification done for xenial:

xenial-updates:

- boots fine w/ console=ttyS0, can ssh in 10 seconds.
- boot fails w/ console=ttyS1, cannot SSH, qemu on 100% CPU (initramfs-tools looping)

xenial-proposed:

- boots fine w/ console=ttyS0, can ssh in 10 seconds. (no regression)
- boots fine w/ console=ttyS1, can ssh in 10 seconds, qemu on low CPU% (issue fixed)

details:
-------

$ lsb_release -cs
xenial

xenial-updates:
---

$ dpkg -s initramfs-tools | grep -i version:
Version: 0.122ubuntu8.16

console=ttyS0:

 $ cat /proc/cmdline
 BOOT_IMAGE=/boot/vmlinuz-4.4.0-184-generic root=UUID=c763ea2f-6085-4419-8895-3cefa32d1477 ro console=ttyS0

console=ttyS1:

 (cannot SSH into system. CPU% always high for QEMU.)

 $ top -b -d1 | grep -e CPU -e qemu
     PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
  143433 libvirt+ 20 0 3886900 366840 22900 S 106.7 2.3 0:32.52 qemu-system-x86
     PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
  143433 libvirt+ 20 0 3886900 366840 22900 S 101.0 2.3 0:33.54 qemu-system-x86
     PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
  143433 libvirt+ 20 0 3886900 366840 22900 S 100.0 2.3 0:34.55 qemu-system-x86
     PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
  143433 libvirt+ 20 0 3886900 366840 22900 S 100.0 2.3 0:35.56 qemu-system-x86
     PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
  143433 libvirt+ 20 0 3886900 366840 22900 S 101.0 2.3 0:36.57 qemu-system-x86
 ^C

xenial-proposed:
---

$ dpkg -s initramfs-tools | grep -i version:
Version: 0.122ubuntu8.17

console=ttyS0:

 $ cat /proc/cmdline
 BOOT_IMAGE=/boot/vmlinuz-4.4.0-184-generic root=UUID=c763ea2f-6085-4419-8895-3cefa32d1477 ro console=ttyS0

console=ttyS1:

 (can SSH into system. CPU% low for QEMU)

 $ cat /proc/cmdline
 BOOT_IMAGE=/boot/vmlinuz-4.4.0-184-generic root=UUID=c763ea2f-6085-4419-8895-3cefa32d1477 ro console=ttyS1

  143646 libvirt+ 20 0 4596800 692248 22972 R 158.4 4.3 0:53.95 qemu-system-x86
     PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
  143646 libvirt+ 20 0 4596800 692248 22972 S 104.0 4.3 0:55.00 qemu-system-x86
     PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
  143646 libvirt+ 20 0 4596800 692248 22972 S 2.0 4.3 0:55.02 qemu-system-x86
     PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
  143646 libvirt+ 20 0 4596800 692248 22972 S 2.0 4.3 0:55.04 qemu-system-x86
     PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
  143646 libvirt+ 20 0 4596800 692248 22972 S 37.3 4.3 0:55.42 qemu-system-x86