kvm_cpuid2_size
cpuid = malloc(kvm_cpuid2_size(nr_entries));
memcpy(vcpu->cpuid, cpuid, kvm_cpuid2_size(cpuid->nent));
memcpy(prev_cpuid, vcpu->cpuid, kvm_cpuid2_size(vcpu->cpuid->nent));
memcpy(prev_cpuid, vcpu->cpuid, kvm_cpuid2_size(vcpu->cpuid->nent));