target-i386/machine: fix migrate faile because of Hyper-V HV_X64_MSR_VP_RUNTIME

target-i386/machine: fix migrate faile because of Hyper-V HV_X64_MSR_VP_RUNTIME

Hyper-V HV_X64_MSR_VP_RUNTIME was introduced in linux-4.4 + qemu-2.5.

As long as the KVM module supports, qemu will save / load the
vmstate_msr_hyperv_runtime register during the migration.

Regardless of whether the hyperv_runtime configuration of x86_cpu_properties is
enabled.

The qemu-2.3 does not support this feature, of course, failed to migrate.

    linux-BGSfqC:/home/qemu # ./x86_64-softmmu/qemu-system-x86_64 --enable-kvm \
        -nodefaults -machine pc-i440fx-2.3,accel=kvm,usb=off -smp 4 -m 4096 -drive \
        file=/work/suse/sles11sp3.img.bak,format=raw,if=none,id=drive-virtio-disk0,cache=none \
        -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x5,drive=drive-virtio-disk0,id=virtio-disk0 \
        -vnc :99 -device cirrus-vga,id=video0,vgamem_mb=8,bus=pci.0,addr=0x2 -monitor vc

    save_section_header:se->section_id=3,se->idstr:ram,se->instance_id=0,se->version_id=4
    save_section_header:se->section_id=0,se->idstr:timer,se->instance_id=0,se->version_id=2
    save_section_header:se->section_id=4,se->idstr:cpu_common,se->instance_id=0,se->version_id=1
    save_section_header:se->section_id=5,se->idstr:cpu,se->instance_id=0,se->version_id=12
    vmstate_subsection_save:vmsd->name:cpu/async_pf_msr
    hyperv_runtime_enable_needed:env->msr_hv_runtime=128902811
    vmstate_subsection_save:vmsd->name:cpu/msr_hyperv_runtime

Since hyperv_runtime is false, vm will not use hv->runtime_offset, then
vmstate_msr_hyperv_runtime is no need to transfer while migrating.

Signed-off-by: ann.zhuangyanying@huawei.com
Message-Id: <1478247398-5016-1-git-send-email-ann.zhuangyanying@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>