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Arm Aims to Secure Its Realm

April 20, 2021

Author: Mike Demler

The next-generation Arm v9-A ISA is that company’s first full architecture increment in 10 years. Despite the big jump from v8 to v9, however, the initial improvements are minor; the first Arm v9-A release is an evolutionary upgrade combining previously announced features. Nevertheless, the intellectual-property (IP) vendor plans to use the v9 umbrella to cover a series of enhancements over the next decade. Arm has yet to disclose a CPU based on the ISA, but MediaTek says it will release a v9-based chip this year. We believe that chip uses the unannounced Matterhorn (Cortex-A79) CPU, which will likely be Arm’s first v9 design.

The initial v9.0-A release will realize the branch target identification (BTI) and Memory Tagging Extension (MTE) that arrived in the 2019 v8.5-A update. BTI prevents jump-oriented-programming (JOP) attacks, and MTE mitigates memory-related security bugs. Arm v9.0-A is also the first release to implement the previously announced Scalable Vector Extension (SVE2) as well as hardware support for the Transactional Memory Extension (TME). It’s unclear whether Matterhorn will include all or just a subset of these features.

Subsequent v9-A releases will feature a much greater security emphasis through the Confidential Compute Architecture (Arm CCA). Arm will roll out further CCA details later this year. Realm, the successor to TrustZone, will also appear as an v9-A feature, but not in the first release, because the company doesn’t plan to publish the specification until July. Licensees will eventually be able to select the optional Realm Management Extension (RME). In addition, the company intends to add ISA features that boost DSP and AI performance. For example, v9.1-A will include Bfloat16 capability and the new general-matrix-multiply (GEMM) instructions first announced for v8.6-A.

Subscribers can view the full article in the Microprocessor Report.

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