This patch fixes an error to boot 32bit vista. The
shadow code uses hvm_get_guest_ctrl_reg(v, 4) to test whether the PAE enabled
But it is not always right. In some cases, when hypervisor
calls hvm_get_guest_ctrl_reg(v, 4) between vmxassist_invoke and
the value of CR4 is not always right. And then the
guest will get wrong shadow modes.
The patch uses the d->arch.hvm_vmx.cpu_state to
test if the PAE is enabled.