Currently, 'vmx->nested.vmxon_ptr' is not reset upon VMXOFF
emulation. This is not a problem per se as we never access
it when !vmx->nested.vmxon. But this should be done to avoid
any issue in the future.

Also, initialize the vmxon_ptr when vcpu is created.
Signed-off-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NYu Zhang <yu.c.zhang@linux.intel.com>
Message-Id: <20210929175154.11396-3-yu.c.zhang@linux.intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>