yahoo-eng-team team mailing list archive

[OpenStack Infra <1759420@xxxxxxxxxxxxxxxxxx>]

Reviewed:  https://review.openstack.org/584999
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=1ba150fa5233ebeacdc02e89b2e83a1a6861bc19
Submitter: Zuul
Branch:    master

commit 1ba150fa5233ebeacdc02e89b2e83a1a6861bc19
Author: Sean Mooney <work@xxxxxxxxxxxxxxx>
Date:   Tue Jul 31 21:22:52 2018 +0100

    libvirt: fix disk_bus handling for root disk
    
    - The hw_disk_bus image metadata key allows users
      to specify the bus to which guest hard disk
      images are attached for libvirt instances.
    
    - In commit 7be531fe9462f2b07d4a1abf6687f649d1dfbb89
      the libvirt disk mappings were refactored. As
      part of that change a lossy conversion was introduced
      which resulted in multiple disk buses being mapped
      to the same block device prefix.
    
    - As a result of this lossy mapping hw_disk_bus=sata
      and hw_disk_bus=usb were mapped to the same prefix
      as scsi "sd". this resulted in the request to use
      sata or usb root disk being ignored.
    
    - This change fixes handling of the root
      disk device bus selection in libvirt blockinfo.py
      by using the disk bus provided instead of inferring
      it from the block device name.
    
    - This change adds a new unit test to
      assert the correct  handeling
      of the hw_disk_bus image metadata key
      in the libvirt driver.
    
    Change-Id: I63836f461507f4924dc8f3491ef518a4ce4d32f9
    Closes-Bug: 1759420


** Changed in: nova
       Status: In Progress => Fix Released

-- 
You received this bug notification because you are a member of Yahoo!
Engineering Team, which is subscribed to OpenStack Compute (nova).
https://bugs.launchpad.net/bugs/1759420

Title:
  nova does not correctly support HW_DISK_BUS=sata or usb for kvm/qemu

Status in OpenStack Compute (nova):
  Fix Released

Bug description:
  Description
  ===========
  The hw_disk_bus image metadata key
  https://github.com/openstack/glance/blob/master/etc/metadefs/compute-libvirt-image.json#L13-L27
  allows users to specify the bus to which guest hard disk images are attched for libvirt instances.

  The valid values of hw_disk_bus are
  ["scsi","virtio","uml","xen","ide","usb","fdc","sata"]

  The libvirt driver also defieds the list of valid buses per virt_type
  here https://github.com/openstack/nova/blob/ef0ce4d692d28a7f5a0079e24acdbfe7d2767e8b/nova/virt/libvirt/blockinfo.py#L199-L206

     valid_bus = {
          'qemu': ['virtio', 'scsi', 'ide', 'usb', 'fdc', 'sata'],
          'kvm': ['virtio', 'scsi', 'ide', 'usb', 'fdc', 'sata'],
          'xen': ['xen', 'ide'],
          'uml': ['uml'],
          'lxc': ['lxc'],
          'parallels': ['ide', 'scsi']
          }

  when setting this key to sata or usb instead of having the disk attached to the requested bus
  the disk is attached to the scsi bus instead.

  this is because in nova/virt/libvirt/blockinfo.py we map form the disk bus to a prefix
  in get_dev_prefix_for_disk_bus
  https://github.com/openstack/nova/blob/ef0ce4d692d28a7f5a0079e24acdbfe7d2767e8b/nova/virt/libvirt/blockinfo.py#L124-L143

  then later we guess what the correct bus is from the prefix in get_disk_bus_for_disk_dev
  https://github.com/openstack/nova/blob/ef0ce4d692d28a7f5a0079e24acdbfe7d2767e8b/nova/virt/libvirt/blockinfo.py#L297-L304

  this mapping form disk bus to prefix is lossy as as sata/scsi and usb
  are all mapped to the sd prefix. so when we guess in
  get_disk_bus_for_disk_dev for kvm that resutin the incorrect value for
  images with hw_disk_bus=sata or hw_disk_bus=usb.

  Steps to reproduce
  ==================
  run devstack with default setting
  source openrc

  set hw_disk_bus=sata on image
  e.g. openstack image set --property hw_disk_bus=sata my-image

  boot a vm with that image
  run virsh dumpxml on instance and check the disk bus.

  Expected result
  ===============
  instance boots and disk bus used matches hw_disk_bus image metadata value.
  e.g. sata

  Actual result
  =============
  instnace boots and disk bus used is scsi

  Environment
  ===========
  1. Exact version of OpenStack you are running. See the following
    stable/pike but this is present in master and has been an issue for 5 years
    since https://github.com/openstack/nova/commit/7be531fe9462f2b07d4a1abf6687f649d1dfbb89#diff-2701504299cd384f46791e08f1849defR293
  incorrectly called get_disk_bus_for_disk_dev instead of useing the disk_bus varible.

  2. Which hypervisor did you use?
     Libvirt + KVM

  2. Which storage type did you use?
     default local image backend for nova.

  3. Which networking type did you use?
     Neutron with OpenVSwitch.
     not related to this issue.

To manage notifications about this bug go to:
https://bugs.launchpad.net/nova/+bug/1759420/+subscriptions