kernel-packages team mailing list archive

[Serge Hallyn <1278531@xxxxxxxxxxxxxxxxxx>]

Screenshot trying to boot a mini-iso from http://archive.ubuntu.com/ubuntu/dists/${release}/main/installer-${arch}/current/iamges/netboot/mini.iso, with both trusty and precise amd64, using command line:

kvm -enable-kvm -drive file=x.img,if=virtio.cache=none -cdrom precise-
mini-amd64.iso -boot d -vnc :1

Running the command inside a 12.04.4 guest on a precise host with trusty
kernel.


** Summary changed:

- nested kvm on saucy kernel hangs
+ nested kvm fails with trust and upstream kernels

** Description changed:

- I have a precise host with saucy ubuntu kernel installed.  I installed
- two VMs there, a saucy and a trusty guest.
+ First: the 3.2 precise kernel handled nested qemu very well.  As of
+ saucy it has declined.
+ 
+ In a host with saucy kernel (even on precise userspace), attempts to do
+ nested kvm result in a hung kvm (inside the guest - host proceeds ok)
+ taking 100%cpu.
+ 
+ In a host with trusty kernel (even on precise userspace), nested kvm
+ fails get past grub.  I have two screenshots, one resulting from
+ attempting to boot from a precise mini-iso, another from attempting to
+ boot a cloud image at:  http://cloud-images.ubuntu.com/quantal/current
+ /quantal-server-cloudimg-amd64-disk1.img.  (If you convert that image to
+ raw, it fails the same way).
+ 
+ On the host, I see the following in /var/log/kern.log: kvm: zapping
+ shadow pages for mmio generation wraparound
+ 
+ I've reproduced this both on (a) a intel based vostro laptop - with
+ separate installs of precise and saucy (with ubuntu precise, saucy,
+ trust, upstream kernels), (b) an intel based server with precise
+ userspace and saucy and trusty kernels;  and (c) an intel laptop running
+ full uptodate trusty.
+ 
+ As nested qemu worked will in the previous LTS, I think it is important
+ to have it working in 14.04 LTS.
+ 
+ ============= Original description ================
+ I have a precise host with saucy ubuntu kernel installed.  I installed two VMs there, a saucy and a trusty guest.
  
  In the saucy guest, non-accelerated qemu works fine, but accelerated kvm
  hangs the first-level saucy guest completely, and pins it at 200% cpu
  usage:
  
     qemu-system-x86 --enable-kvm -monitor stdio -vnc :1
  
  On the trusty guest it works just fine.

** Attachment added: "screenshot1.png"
   https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1278531/+attachment/3994631/+files/screenshot1.png

-- 
You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/1278531

Title:
  nested kvm fails with trust and upstream kernels

Status in “linux” package in Ubuntu:
  Confirmed

Bug description:
  First: the 3.2 precise kernel handled nested qemu very well.  As of
  saucy it has declined.

  In a host with saucy kernel (even on precise userspace), attempts to
  do nested kvm result in a hung kvm (inside the guest - host proceeds
  ok) taking 100%cpu.

  In a host with trusty kernel (even on precise userspace), nested kvm
  fails get past grub.  I have two screenshots, one resulting from
  attempting to boot from a precise mini-iso, another from attempting to
  boot a cloud image at:  http://cloud-images.ubuntu.com/quantal/current
  /quantal-server-cloudimg-amd64-disk1.img.  (If you convert that image
  to raw, it fails the same way).

  On the host, I see the following in /var/log/kern.log: kvm: zapping
  shadow pages for mmio generation wraparound

  I've reproduced this both on (a) a intel based vostro laptop - with
  separate installs of precise and saucy (with ubuntu precise, saucy,
  trust, upstream kernels), (b) an intel based server with precise
  userspace and saucy and trusty kernels;  and (c) an intel laptop
  running full uptodate trusty.

  As nested qemu worked will in the previous LTS, I think it is
  important to have it working in 14.04 LTS.

  ============= Original description ================
  I have a precise host with saucy ubuntu kernel installed.  I installed two VMs there, a saucy and a trusty guest.

  In the saucy guest, non-accelerated qemu works fine, but accelerated
  kvm hangs the first-level saucy guest completely, and pins it at 200%
  cpu usage:

     qemu-system-x86 --enable-kvm -monitor stdio -vnc :1

  On the trusty guest it works just fine.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1278531/+subscriptions