AN ASYNCHRONOUS BUS BRIDGE FOR PARTITIONED MULTI-SOC ARCHITECTURES ON FPGAS

REPORTER: HSUAN- JU L I2014/04/09

Field Programmable Logic and Applications (FPL), 2013 23rd International Conference on, Sept. (2013)

Daniel Kliem, Sven-Ole Voigt

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OutlineIntroductionArchitecture And Related WorkAsynchronous Secure BridgeMulti-System FPGA DesignsBenchmarks Results And DiscussionConclusion

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OutlineIntroductionArchitecture And Related WorkAsynchronous Secure BridgeMulti-System FPGA DesignsBenchmarks Results And DiscussionConclusion

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Introduction Software applications of safety- and security-critical embedded systems are often divided into several self-contained functions.

Between individual system partitions and functions.We use segregation to confine error propagation.

Soft processors are one order of magnitude slower in terms of operating frequency than hard-wired devices.

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Introduction(cont.) Current FPGA families provide wide and fast memory attachments mostly implemented as hard macros that are faster than configurable logic.There is a performance gap between soft processors and the

memory attachment.Propose an architecture combines : The specific needs of partitioned software.The flexibility of reconfigurable hardware.

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Introduction(cont.) Multiple self-contained systems on a single platform FPGAShares available memory bandwidth among the systems In a predictable and scalable way.

The main building blocks of the proposed architectureSecure bus bridges that are used to form a segregated hierarchy

of memory busses.

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Introduction(cont.) With secure bus bridges, it is possible to use soft processors for safety and security-critical functions.To reach high assurance levels with far less effort.

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OutlineIntroductionArchitecture And Related WorkAsynchronous Secure BridgeMulti-System FPGA DesignsBenchmarks Results And DiscussionConclusion

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Architecture And Related Work Architecture that achieves domain segregation with Secure Bus Bridges. On-chip

(Replicated local resources)

Off-chip(Shared for cost

reduction.)

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Architecture And Related Work(cont.) Multi-Processor SoCs(MPSoCs) often comprise shared caches.

CPUs and I/O units that are assigned to one particular software functionInfluence execution times of other functions on different cores.

The Worst-Case Execution Time (WCET) of real-time applications on MPSoCs is less predictable

MPSoCs with Multi-Port Memory Controllers (MPMCs)Connecting the local systems to individual ports.Would be scalable in terms of performance.

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Architecture And Related Work(cont.) Backbone-based approach is modular and uses individually verifiable SECBRGsKeep segregation and memory attachment in different places.

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Architecture And Related Work(cont.) Local

resources exclusively

used

Neither interrupts nor interface overload

propagate into neighboring systems.

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Architecture And Related Work(cont.)

Necessary spatial

segregation by address

translation.

Non-overlapping

memory partitions Caching can be implemented without coherency

support between different bridges!!

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Architecture And Related Work(cont.) If the backbone bandwidth was larger than the accumulated local bus bandwidths.Multi-system architecture would scale perfectly.The asynchronous SECBRGs can connect the local busses to wider

and faster backbones.Memory access temporal conflicts occur at a lower rate. Scalability for multiple local systems is ensured.

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OutlineIntroductionArchitecture And Related WorkAsynchronous Secure BridgeMulti-System FPGA DesignsBenchmarks Results And DiscussionConclusion

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Asynchronous Secure Bridge

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Asynchronous Secure Bridge(cont.)-Command Queue and Result Queue

Implemented as FPGA-specific hard

macro blocks (BRAMs)

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Asynchronous Secure Bridge(cont.)-Address Translation unit

Exclusive non-overlapping main memory areas (spatial segregation).

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Asynchronous Secure Bridge(cont.)-Bridge Slave and Cache Controller (BSCC)

Copy-back caching strategy with valid and dirty flags

Cache hit: Local accesses are directly serviced by the BSCC.

Cache miss: Fetch commands are placed into the CQ.(Address and size of the data)

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Asynchronous Secure Bridge(cont.)-Burst Unit (BU)

Expands the fetch commands from CQ to multiple sequential read operations (bursts).

Provides them to the BridgeMaster Controller (BMC).

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Asynchronous Secure Bridge(cont.)-Case of cache cell replacement(to service a cache miss)

Fetch and write commands are finally issued out-of-order by the BMC.

The BSCC can proceed with the replacement operation of a cache line while the BMC services the previous fetch.

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Asynchronous Secure Bridge(cont.)-Case of cache cell replacement(to service a cache miss)

Although the BSCC blocks the waiting local master until fetched data arrives in the RQ. It does not wait until all write commands are serviced by the BMC Queue latency does not block the cache with this scheme.

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Asynchronous Secure Bridge(cont.) To reduce backbone utilization and to achieve scalable performance.Caching, bursting, out-of-order prefetching, and different clock

ratios are used. To ensures exclusive access to memory locations.Copy-back caching and out-of-order issuing is possible.

Complex cache coherence mechanisms are avoided which leads to simpler and more scalable system designs.

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OutlineIntroductionArchitecture And Related WorkAsynchronous Secure BridgeMulti-System FPGA DesignsBenchmarks Results And DiscussionConclusion

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Multi-System FPGA Designs Asynchronous secure bridges Without relaxing the timing constraints Improves place-and-route even when the same frequency is used in

all domains.Local busses and the backbone can be driven by independent

clocks.

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Multi-System FPGA Designs(cont.) Prototype implementations on the open source VHDL IP-core library GRLIB by Aeroflex Gaisler. Xilinx ML605 board (Virtex 6 LX240T).One- to eight-fold GRLIB-based prototype designs with clock frequencies as high as 133 MHz.

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OutlineIntroductionArchitecture And Related WorkAsynchronous Secure BridgeMulti-System FPGA DesignsBenchmarks Results And DiscussionConclusion

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Benchmarks Results And Discussion The Relative Execution Time (RET) and the Backbone Idle Ratio (BIR)RET: The quotient of the measured local clock ticks spent by a

benchmark program divided by a reference tick value.BIR: Relates the idle cycles of the backbone to the total amount of

cycles at backbone frequency.

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Benchmarks Results And Discussion(cont.) T

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OutlineIntroductionArchitecture And Related WorkAsynchronous Secure BridgeMulti-System FPGA DesignsBenchmarks Results And DiscussionConclusion

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Conclusion A novel design of an asynchronous secure bus bridge that partitions multi-SoC FPGA designs into multiple clock domains and reliably shares available bandwidth among multiple soft processor system. Individual clock domains ensure repeatable place-and-route results that scale well with increasing numbers of local systems. The proposed architecture is able to overcome this bandwidth gap and to put soft processors to practical use for safety- and security-critical applications.

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