This bug was fixed in the package linux - 3.13.0-15.35
---------------
linux (3.13.0-15.35) trusty; urgency=low
[ Tim Gardner ]
* Release Tracking Bug
- LP: #1287175
[ Andy Whitcroft ]
* [Config] tools -- enable cpupower on ppc64el
* [Config] ppc64el -- enable perf tools
* [Config] powerpc -- enable perf tools
* [Config] ppc64el -- reduce MAX_ORDER with 64k pages
* [Config] ppc64el -- switch to 64K system pages
[ Benjamin Herrenschmidt ]
* SAUCE: powerpc/powernv: Add iommu DMA bypass support for IODA2
[ Paul Mackerras ]
* SAUCE: powerpc: Increase stack redzone for 64-bit userspace to 512
bytes
[ Upstream Kernel Changes ]
* perf trace: Fix ioctl 'request' beautifier build problems on !(i386 ||
x86_64) arches
* kvm, vmx: Really fix lazy FPU on nested guest
- LP: #1278531
-- Tim Gardner <tim.gard...@canonical.com> Mon, 03 Mar 2014 13:22:56 +0000
** Changed in: linux (Ubuntu Trusty)
Status: Fix Committed => Fix Released
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https://bugs.launchpad.net/bugs/1278531
Title:
nested kvm fails with trusty and upstream kernels
Status in “linux” package in Ubuntu:
Fix Released
Status in “linux” source package in Trusty:
Fix Released
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.
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