[Bug 63131] New: guest hang when reboot .

[Bug 63131] New: guest hang when reboot .

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=63131

            Bug ID: 63131
           Summary: guest hang when reboot .
           Product: Virtualization
           Version: unspecified
    Kernel Version: 3.12.0-rc2
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: kvm
          Assignee: virtualization_kvm@kernel-bugs.osdl.org
          Reporter: chao.zhou@intel.com
        Regression: No

Environment:
------------
Host OS (ia32/ia32e/IA64):ia32e
Guest OS (ia32/ia32e/IA64):ia32e
Guest OS Type (Linux/Windows):Windows
kvm.git Commit:7854cbca815562a49d50bbc6f31599312853d1f4
qemu.git Commit:1cdae4573d7613149348d834c605bfbe3c7d405b
Host Kernel Version:3.12.0-rc2
Hardware: Romley_EP


Bug detailed description:
--------------------------
create guest then reboot ,the guest will hang

note 
1.try win7, win8, win2012,win2k8 and rhel6u4 guest, while reboot,guest will
hang
2.when create guest with "-cpu host" the guest reboot pass
3.This should be a kernel bug
kvm      + qemu     =  result
7854cbca + 1cdae457 =  bad
2f303b74 + 1cdae457 =  good

Reproduce steps:
----------------
1.create guest
qemu-system-x86_64 -enable-kvm -m 2048 -smp 2 -net none win7.qcow

2.reboot the guest

Current result:
----------------
guest hang

Expected result:
----------------
guest can work well while reboot

Basic root-causing log:

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[Bug 63131] guest hang when reboot .

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=63131

--- Comment #1 from Zhou, Chao <chao.zhou@intel.com> ---
the first bad commit is
commit d7876f1be40a16223a44355740de625849504eb5
Author: Paolo Bonzini <pbonzini@redhat.com>
Date:   Wed Oct 2 16:06:15 2013 +0200

    KVM: x86: prevent setting unsupported XSAVE states

    A guest can still attempt to save and restore XSAVE states even if they
    have been masked in CPUID leaf 0Dh.  This usually is not visible to
    the guest, but is still wrong: "Any attempt to set a reserved bit (as
    determined by the contents of EAX and EDX after executing CPUID with
    EAX=0DH, ECX= 0H) in XCR0 for a given processor will result in a #GP
    exception".

    The patch also performs the same checks as __kvm_set_xcr in KVM_SET_XSAVE.
    This catches migration from newer to older kernel/processor before the
    guest starts running.

    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: Gleb Natapov <gleb@redhat.com>

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[Bug 63131] guest hang when reboot .

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https://bugzilla.kernel.org/show_bug.cgi?id=63131

Paolo Bonzini <bonzini@gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bonzini@gnu.org

--- Comment #2 from Paolo Bonzini <bonzini@gnu.org> ---
Reproduced on Ivy Bridge host with "-cpu Westmere", passes with "-cpu
SandyBridge".

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[Bug 63131] guest hang when reboot .

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https://bugzilla.kernel.org/show_bug.cgi?id=63131

Zhou, Chao <chao.zhou@intel.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |CODE_FIX

--- Comment #3 from Zhou, Chao <chao.zhou@intel.com> ---
this commit fix the bug:
commit 46c34cb059d519601fb567b55cf45c300fea2928
Author: Paolo Bonzini <pbonzini@redhat.com>
Date:   Thu Oct 17 16:50:46 2013 +0200

    KVM: x86: fix KVM_SET_XCRS for CPUs that do not support XSAVE

    The KVM_SET_XCRS ioctl must accept anything that KVM_GET_XCRS
    could return.  XCR0's bit 0 is always 1 in real processors with
    XSAVE, and KVM_GET_XCRS will always leave bit 0 set even if the
    emulated processor does not have XSAVE.  So, KVM_SET_XCRS must
    ignore that bit when checking for attempts to enable unsupported
    save states.

    Reviewed-by: Gleb Natapov <gleb@redhat.com>
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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[Bug 63131] guest hang when reboot .

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https://bugzilla.kernel.org/show_bug.cgi?id=63131

Zhou, Chao <chao.zhou@intel.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |VERIFIED

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