[Bug 58921] New: [nested virt] L2 Windows guest can't boot up ('-cpu host' to start L1)

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https://bugzilla.kernel.org/show_bug.cgi?id=58921

           Summary: [nested virt] L2 Windows guest can't boot up ('-cpu
                    host' to start L1)
           Product: Virtualization
           Version: unspecified
    Kernel Version: 3.10.0-rc1
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: kvm
        AssignedTo: virtualization_kvm@kernel-bugs.osdl.org
        ReportedBy: yongjie.ren@intel.com
        Regression: Yes


Environment:
------------
Host OS (ia32/ia32e/IA64):ia32e
Guest OS (ia32/ia32e/IA64):ia32e
Guest OS Type (Linux/Windows): Windows
kvm.git next branch Commit:db6ae6158186a17
qemu-kvm Commit:b5803aa3583e82e513
Host Kernel Version:3.9.0-rc3
Hardware:SandyBridge-EP


Bug detailed description:
--------------------------
In 'kvm on kvm' nested virtualization environment,if I start L1 with '-cpu
host', a Windows (e.g. Win7) guest can't boot up as L2 guest.

note: 
1. when creating a linux guest as L2 guest, L2 guest boot up fine
2. if starting L1 with '-cpu qemu64,+vmx', L2 Windows can boot up.
3. this should be a kvm kernel bug:
kvm next + qemu-kvm   =  result
db6ae615 + b5803aa3   = bad
188424ba + b5803aa3   = good

Reproduce steps:
----------------
1.create L1 guests:
qemu-system-x86_64 --enable-kvm -m 10240 -smp 8 -net
nic,macaddr=00:12:45:67:2B:1C -net tap,script=/etc/kvm/qemu-ifup
nested-kvm-rhel6u4.qcow -cpu host
2. create L2 guests:
qemu-system-x86_64 -enable-kvm -m 1024 -smp 2 -net none win7.img


Current result:
----------------
L2 guest (win7 guest) failed to boot up.

Expected result:
----------------
L2 guest (win7 guest) boot up fine

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