[Bug 1680956] Re: Fail to launch an OpenStack Instance with hugepages on top of OVS+DPDK

[ChristianEhrhardt]

I already had the patch complete and was writing the changelog, but
while doing that and the dep8 header I realized that this really isn't
something we want to do.

Effectively that would "invite" latter and worse issues - in this case for example you don't want qemu to map against the 1G pages in /dev/hugepages-1048576.
You really might want to uncomment the hugetlbfs_mount in /etc/libvirt/qemu.conf to disable the guesswork libvirt is doing.
If you would really want it to map against that you'd still want to set hugetlbfs_mount to have it reliably pick up the right path and in case of a non standard path you'd then want to extend the apparmor profile as Seth suggested.

I still want to continue discussing this and it would be great Thiago,
if you could provide the files I asked for of your case. Also I might
overlook something, so discussion is certainly worth it.

I'll however make a comment entry in the DPDK config file about the issue.
Adding a tracker now.

** Also affects: dpdk (Ubuntu)
   Importance: Undecided
       Status: New

** Changed in: dpdk (Ubuntu)
       Status: New => Triaged

** Changed in: dpdk (Ubuntu)
   Importance: Undecided => Low

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https://bugs.launchpad.net/bugs/1680956

Title:
  Fail to launch an OpenStack Instance with hugepages on top of OVS+DPDK

Status in Ubuntu Cloud Archive:
  New
Status in dpdk package in Ubuntu:
  Triaged
Status in libvirt package in Ubuntu:
  Incomplete

Bug description:
  Guys,

   I'm trying to launch an Instance on OpenStack Ocata, using Ubuntu
  16.04, on top of OpenvSwitch with DPDK, and OVN.

   I can launch an Instance without hugepages but, when I change
  OpenStack's Flavor for it to have: "hw:mem_size_pages=large", the
  following error appear on nova-compute.log:

  
  ---
  2017-04-07 20:13:18.504 3996 ERROR nova.compute.manager [instance: fbbb7bde-763e-40d3-8987-fb3a6c568ad8] libvirtError: internal error: process exited while connecting to monitor: 2017-04-07T20:13:17.764939Z qemu-system-x86_64: -object memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/dev/hugepages-1048576/libvirt/qemu,share=yes,size=4294967296,host-nodes=0,policy=bind: can't open backing store /dev/hugepages-1048576/libvirt/qemu for guest RAM: Permission denied
  ---

  At syslog:

  ---
  Apr 7 20:13:17 expert-jennet kernel: [ 1535.437956] audit: type=1400 audit(1491595997.759:23): apparmor="DENIED" operation="mknod" profile="libvirt-fbbb7bde-763e-40d3-8987-fb3a6c568ad8" name="/dev/hugepages-1048576/libvirt/qemu/qemu_back_mem._objects_ram-node0.BFNx2W" pid=8341 comm="qemu-system-x86" requested_mask="c" denied_mask="c" fsuid=64055 ouid=64055
  ---

  Maybe it is related to:

  https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1524737

  But I'm not sure if it is relate to 1524737 or not...

  Let me know if there are any workarounds available!

  Thanks,
  Thiago

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: libvirt0 2.5.0-3ubuntu5~cloud0 [origin: Canonical]
  ProcVersionSignature: Ubuntu 4.8.0-46.49~16.04.1-generic 4.8.17
  Uname: Linux 4.8.0-46-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2.5
  Architecture: amd64
  CrashDB:
   {
                  "impl": "launchpad",
                  "project": "cloud-archive",
                  "bug_pattern_url": "http://people.canonical.com/~ubuntu-archive/bugpatterns/bugpatterns.xml",
               }
  Date: Fri Apr  7 20:27:27 2017
  ProcEnviron:
   TERM=screen
   PATH=(custom, no user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: libvirt
  UpgradeStatus: No upgrade log present (probably fresh install)

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