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[Chris J Arges <1479031@xxxxxxxxxxxxxxxxxx>]

Problem exists between v3.9 and v3.10.

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https://bugs.launchpad.net/bugs/1479031

Title:
  attached block devices not showing up

Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Precise:
  Confirmed

Bug description:
  I have Ubuntu Precise guests running in kvm to which I attach volumes
  immediately after boot. Sometimes I notice that the devices do not
  show up in the guest e.g. they are not visible in /proc/partitions and
  dmesg boot log shows no sign of then being noticed. Qemu itself shows
  that the devices are attached and if I do a rescan within the guest
  the devices appear. A reboot also cause the devices to appear. So, it
  feels like there is enough evidence to suggest that the devices were
  properly attached by qemu/seabios but they just didn't get noticed by
  the guest.

  This issue is reproducible with Precise running 3.2, 3.5 (lts-quantal)
  and 3.8 (lts-raring) kernels but not as of 3.11 (lts-saucy) so it
  would appear that something changed between 3.8 and 3.11 that resolved
  this issue and if we can identify it we should backport to 3.2.

  I am able to reproduce this issue using Openstack to spin up vms and
  attach volumes using the following script:

  http://pastebin.ubuntu.com/11954253/

  I hit this issue with 1/2 instances.

  As a workaround one can rescan and the device shows up:
  echo 1 | sudo tee /sys/bus/pci/rescan

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