if (xen_feature(XENFEAT_mmu_pt_update_preserve_ad)) {
pv_mmu_ops.ptep_modify_prot_start = xen_ptep_modify_prot_start;
pv_mmu_ops.ptep_modify_prot_commit = xen_ptep_modify_prot_commit;
if (xen_feature(XENFEAT_mmu_pt_update_preserve_ad)) {
pv_mmu_ops.ptep_modify_prot_start = xen_ptep_modify_prot_start;
pv_mmu_ops.ptep_modify_prot_commit = xen_ptep_modify_prot_commit;