xstate_required_size
entry->ebx = xstate_required_size(permitted_xcr0, false);
entry->ebx = xstate_required_size(permitted_xcr0 | permitted_xss,
best->ebx = xstate_required_size(vcpu->arch.xcr0, false);
best->ebx = xstate_required_size(vcpu->arch.xcr0 |
u32 xstate_required_size(u64 xstate_bv, bool compacted);
r = xstate_required_size(kvm_get_filtered_xcr0(), false);