From mboxrd@z Thu Jan  1 00:00:00 1970
From: bugzilla-daemon@bugzilla.kernel.org
Subject: [Bug 43068] New: Operation restricted to levels L0-2 - kerneloops
 when booting L3
Date: Sat, 7 Apr 2012 17:36:23 GMT
Message-ID: <bug-43068-28872@https.bugzilla.kernel.org/>
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https://bugzilla.kernel.org/show_bug.cgi?id=43068

           Summary: Operation restricted to levels L0-2 - kerneloops when
                    booting L3
           Product: Virtualization
           Version: unspecified
    Kernel Version: 3.2.0-2-amd64
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: kvm
        AssignedTo: virtualization_kvm@kernel-bugs.osdl.org
        ReportedBy: 2005@kuarepoti-dju.net
        Regression: No


Created an attachment (id=72845)
 --> (https://bugzilla.kernel.org/attachment.cgi?id=72845)
Kernel oops backtrace

Trying to run KVM with a high level of nesting works fine for the first two
levels of virtual machines (L1 and L2) but leads to the attached oops when
attempting to boot into L3.

The host system has 24 Xeon X5675 cores running Ubuntu 12.04 with kernel
3.2.0-21-generic. The nested VMs are restricted to one of these core. They all
run resized clones of a Debian wheezy (testing) image with kernel
3.2.0-2-amd64.

In the Turtles paper, nested virtualisation has been presented to support Ln
and includes L3 in the diagrams but the evaluation only went up to L2. The
kernel documentation nested-vmx.txt doesn't list this as a restriction but
doesn't mention L3 or higher either. Hence, it is not clear if the
implementation is supposed to support L3 at all, at the moment or in the
foreseeable future.

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