  Since its public introduction in the mid-2010s, the Row Hammer (RH)
phenomenon has drawn significant attention from the research community due to
its security implications. Although many RH-protection schemes have been
proposed by processor vendors, DRAM manufacturers, and academia, they still
have shortcomings. Solutions implemented in the memory controller (MC) incur
increasingly higher costs due to their conservative design for the worst case
in terms of the number of DRAM banks and RH threshold to support. Meanwhile,
DRAM-side implementation either has a limited time margin for RH-protection
measures or requires extensive modifications to the standard DRAM interface.
Recently, a new command for RH-protection has been introduced in the
DDR5/LPDDR5 standards, referred to as refresh management (RFM). RFM enables the
separation of the tasks for RHprotection to both MC and DRAM by having the
former generate an RFM command at a specific activation frequency and the
latter take proper RH-protection measures within a given time window. Although
promising, no existing study presents and analyzes RFM-based solutions for
RH-protection. In this paper, we propose Mithril, the first RFM
interfacecompatible, DRAM-MC cooperative RH-protection scheme providing
deterministic protection guarantees. Mithril has minimal energy overheads for
common use cases without adversarial memory access patterns. We also introduce
Mithril+, an optional extension to provide minimal performance overheads at the
expense of a tiny modification to the MC, while utilizing existing DRAM
commands.
