Cosmic X-ray surveys over the past two decades have played a critical role in transforming our understanding of growing supermassive black holes (SMBHs) in the distant universe. I will describe one key program, now recently completed, advancing this effort, the 12 deg2 XMM-SERVS survey. XMM-SERVS has successfully mapped three legacy sky regions at 50 ks depth: the SERVS areas of CDF-S, XMM-LSS, and ELAIS-S1. These regions have first-rate multiwavelength coverage already and are LSST/DES Deep-Drilling Fields, MOONS/PFS massive spectroscopy fields, prime TolTEC/ALMA fields, and multi-object reverberation-mapping fields. When the follow-up of its 11,000 X-ray sources is complete, XMM-SERVS should dramatically advance studies of SMBH growth across the full range of cosmic environments, links between SMBH accretion and host-galaxy properties, groups/clusters at z = 0.1-2, protoclusters, and other topics. I will also describe some valuable optical/infrared photometric and photometric-redshift datasets generated as part of XMM-SERVS.