System Memory Management Units

The Arm System Memory Management Units

About System Memory Management Units

A system memory management unit (SMMU) is responsible for all aspects of memory management, including caching and memory virtualization. It gives a common view of memory to all SoC components. It enforces memory protection and access schematic while extending memory virtualization services that match those provided by the main application processor to ensure consistent security across the SoC. The SMMU is designed for use in a virtualized system where multiple guest operating systems are managed by a hypervisor. 


The System Memory Management Unit family

CoreLink MMU-600

Highly scalable and support for millions of translation contexts.

The CoreLink MMU-600 is compatible with the Armv8.2-A enabled Cortex-A75 and Cortex-A55 processors, and is backwards compatible with Armv7 and Armv8 processors. Designs can be scaled from small to large-scale systems while maintaining a common driver framework. 

Support for PCIe Gen4 enables IO accelerators to be connected for high throughput systems. 

CoreLink MMU-600’s stage 2 protection mechanism also enables TrustZone Media Protection v2 (TZMP2) with master side filtering. This protects high value 4K premium content without the need for extensive memory carve-outs.

CoreLink MMU-500

Accelerated stage 1 and stage 2 address translation for maximum flexibility.

The CoreLink MMU-500 is compatible with the Armv8-A enabled Cortex-A72 and Cortex-A53 processors, and is backwards compatible with the Arm Cortex-A15 and Arm Cortex-A7 processors. It offers nested stage 1 and stage 2 accelerated address translation with multiple distributed translation buffers controlled from a single control unit. It is compatible with a wide range of bus master types and capabilities. offering maximum flexibility in implementing efficient SoC designs that need to support virtualized applications.

CoreLink MMU-401

Accelerated stage 2 address translation to reduce hypervisor overhead.

The CoreLink MMU-401 is compatible with the Arm Cortex-A15 and Cortex-A7 processors and offers stage 2 accelerated address translation for bus masters that already implement MMU functionality for stage 1 translation, such as the Mali-400 Graphics Processor, thereby reducing the hypervisor overhead in managing complex bus master interactions.

 

Highlights

CoreLink MMU-600 Features

  • Enhances CoreLink MMU-500 feature set by incorporating SMMUv3.1 specification to support Armv8.2 CPUs.
  • Expands the number of contexts supported to millions.
  • Implements AMBA-DTI to interface TBU and TCU to improve scalability.

 

  • Multi-level TLB and Walk Cache improves system address translation hit rates.
  • Improved write buffer depth and parallel translations.
Enterprise server system example

CoreLink MMU-500 Features

  • Builds on top of MMU-400 features by implementing SMMUv2 architecture adding support for Armv8 CPUs.
  • Supports Stage 1, Stage 2, and Stage1 followed by Stage 2 address translation for up to 128 active device contexts.
  • Implements a distributed Translation Buffer Unit (TBU) micro-architecture with direct point-to-point connections between each TBU and the centralized Translation Control Unit (TCU) for Page Table Walks (PTWs).
  • Supports up to 128 entries per TLB which is further backed by TCU cache up to 2K entries.

CoreLink MMU-401 Features

  • Supports SMMUv1 architecture for Armv7 CPUs and Arm v8 for 64KB page sizes.
  • Performs stage2 translation only for hypervisor support.
  • Implements a single TBU micro-architecture with connection to a single TCU for page table walks.

CoreLink MMU-500 Characteristics

The CoreLink MMU-500 supports the translation formats of Armv7 and Armv8 architectures and performs Stage 1, Stage 2, or Stage 1 followed by Stage 2 translations for all page sizes except 16KB page granule for Armv8. The MMU-500 is implemented as a distributed design with one or more TBUs communicating to a single centralized TCU that performs PTWs to memory. Each TBU can be located in its own clock and power domain making it easy to co-locate the TBU with the peripheral requiring translation. Each TBU communicates to the TCU over an point-to-point stream interface and with bus masters over ACE-Lite. The TCU has an AXI4 slave interface for configuration. 


Important Documentation

  • CoreLink MMU-600 Technical Reference Manual

    For system designers, system integrators and programmers who are designing a SoC, the Technical Reference Manual is the go-to resource.

    MMU-600 TRM
  • CoreLink MMU-500 Technical Reference Manual

    For system designers, system integrators and programmers who are designing a SoC, the Technical Reference Manual is the go-to resource.

    MMU-500 TRM
  • CoreLink MMU-401 Technical Reference Manual

    For system designers, system integrators and programmers who are designing a SoC, the Technical Reference Manual is the go-to resource.

    MMU-401 TRM
  • SMMUv3 Architecture Spec

    Builds on top of SMMUv2 specification to add support for Armv8 architecture.


    SMMUv3 Spec