Designing soft-errors resilient systems is a complex engineering task, which nowadays follows a cross-layer approach. It requires a careful planning for different fault-tolerance mechanisms at different system's layers: starting from the technology up to the software domain. While these design decisions have a positive effect on the reliability of the system, they usually have a detrimental effect on its size, power consumption, performance and cost. Design space exploration for cross-layer reliability is therefore a multi-objective search problem in which reliability must be traded-off with other design dimensions. Assessing the reliability of a complex system and performing design space exploration in the early phases of the design cycle is a complex task and designers are increasing looking at stochastic models able to provide fast results to quickly drive early design decisions. This paper summarizes some of the results achieved by the authors in more than five years of research in this domain.

Cross-layer reliability is becoming the preferred solution when reliability is a concern in the design of a microprocessor-based system. Nevertheless, deciding how to distribute the error management across the different layers of the system is a very complex task that requires the support of dedicated frameworks for cross-layer reliability analysis. This paper proposes SyRA, a system-level cross-layer early reliability analysis framework for radiation induced soft errors in memory arrays of microprocessor-based systems. The framework exploits a multi-level hybrid Bayesian model to describe the target system and takes advantage of Bayesian inference to estimate different reliability metrics. SyRA implements several mechanisms and features to deal with the complexity of realistic models and implements a complete tool-chain that scales efficiently with the complexity of the system. The simulation time is significantly lower than micro-architecture level or RTL fault-injection experiments with an accuracy high enough to take effective design decisions. To demonstrate the capability of SyRA, we analyzed the reliability of a set of microprocessor-based systems characterized by different microprocessor architectures (i.e., Intel x86, ARM Cortex-A15, ARM Cortex-A9) running both the Linux operating system or bare metal in the presence of single bit upsets caused by radiation induced soft errors. Each system under analysis executes different software workloads both from benchmark suites and from real applications.

Recent years have witnessed the growth of the adoption of Cyber-Physical Systems (CPSs) in many sectors such as automotive, aerospace, civil infrastructures and healthcare. Several CPS applications include critical scenarios, where a failure of the system can lead to catastrophic consequences. Therefore, anomalies due to failure or malicious attacks must be timely detected. This paper focuses on two relevant aspects of the design of a CPS: safety and security. In particular, it studies how performance monitor counters (PMCs) available in modern microprocessors can be from the one hand a valuable tool to enhance the safety of a system and, on the other hand, a security backdoor. Starting from the example of a PMC based safety mechanism, the paper shows the implementation of a possible attack and eventually proposes a strategy to mitigate the effectiveness of the attack while preserving the safeness of the system.

State-of-the-art GPU chips are designed to deliver extreme throughput for graphics as well as for data-parallel general purpose computing workloads (GPGPU computing). Unlike computing for graphics, GPGPU computing requires highly reliable operations. Since provisioning for high reliability may affect performance, the design of GPGPU systems requires the vulnerability of GPU workloads to soft-errors to be jointly evaluated with the performance of GPU chips. We present an extended study based on a consolidated workflow for the evaluation of the reliability in correlation with the performance of four GPU architectures and corresponding chips: AMD Southern Islands and NVIDIA G80/GT200/Fermi. We obtained reliability measurements (AVF and FIT) employing both fault injection and ACE-analysis based on microarchitecture-level simulators. Apart from the reliability-only and performance-only measurements, we propose combined metrics for performance and reliability that assist comparisons for the same application among GPU chips of different ISAs and vendors, as well as among benchmarks on the same GPU chip.

Designing soft errors resilient systems is a complex engineering task, which nowadays follows a cross-layer approach. It requires a careful planning for different fault-tolerance mechanisms at different system's layers: starting from the technology up to the software domain. While these design decisions have a positive effect on the reliability of the system, they usually have a detrimental effect on its size, power consumption, performance and cost. Design space exploration for cross-layer reliability is therefore a multi-objective search problem in which reliability must be traded-off with other design dimensions. This paper proposes a cross-layer multi-objective design space exploration algorithm developed to help designers when building soft error resilient electronic systems. The algorithm exploits a system-level Bayesian reliability estimation model to analyze the effect of different cross-layer combinations of protection mechanisms on the reliability of the full system. A new heuristic based on the extremal optimization theory is used to efficiently explore the design space. Two exploration strategies are proposed. The first strategy aims at optimizing the reliability of the system alone. It is suited in those cases in which reaching a given reliability target is the sole goal. It focuses on finding a reduced set of system's components that, when protected, allow the designer to reach the desired reliability level. As a positive effect, by reducing the number of protected components, the overhead introduced by the fault tolerance techniques is reduced as well. The second strategy jointly considers the effect that the introduced fault-tolerance mechanisms have on the execution time, power, hardware area and software size. This strategy supports the exploration of the design space setting multiple objectives on different design dimensions. An extended set of simulations shows the capability of this framework when applied both to benchmark applications and realistic systems, providing optimized systems that outperform those obtained by applying state-of-the-art cross-layer reliability techniques.

General Purpose computing on Graphics Processing Unit offers a remarkable speedup for data parallel workloads, leveraging GPUs computational power. However, differently from graphic computing, it requires highly reliable operation in several application domains. In this paper we present SIFI a reliability evaluation framework for soft-errors on AMD GPUs built on top of Multi2Sim, a micro-architectural level simulator. SIFI is capable of computing different reliability metrics by means of two different techniques: fault injection and ACE analysis. Experiments performed on a set of 14 GPGPU applications targeting the AMD Southern Islands GPU architecture show the capability of the tool and the potential of its use to support decisions about the best architectural parameters for a given application.

State-of-the-art GPU chips are designed to deliver extreme throughput for graphics as well as for data-parallel general purpose computing workloads (GPGPU computing). Unlike graphics computing, GPGPU computing requires highly reliable operation. The performance-oriented design of GPUs requires to jointly evaluate the vulnerability of GPU workloads to soft-errors with the performance of GPU chips. We briefly present a summary of the findings of an extensive study aiming at the evaluation of the reliability of four GPU architectures and corresponding chips, orrelating them with the performance of the workloads.

This paper describes the joint effort of the two FP7 EU projects CLERECO and MoRV toward the definition of an extended reliability information exchange format able to manage reliability information for the full system stack, from technology up to the software level. The paper starts from the RIIF language initiative, proposing a set of new features to improve the expression power of the language and to extend it to the software layer of a system. The proposed extended reliability information exchange format named RIIF-2 has the potential to support the development of next generation reliability analysis tools that will help to fully include reliability evaluation into an automated design flow, pushing cross-layer reliability considerations at the same level of importance as area, timing and power consumption when performing design exploration for new products.

Integration of nanowire structures in more complex platforms combining microfluidics and multiplexing aspects may complex the electrical readout process. In the present work, fabrication of Aluminium (Al) lines for electrical connections is attempted followed by their integration to nanofabricated Memristive Biosensors that target at the label-free detection of cancer biomarkers. In addition a computational study is carried out investigating the impact of the resistance introduced by the additional Al connections to the electrical response of the Memristive Biosensors. Overall, the present study explores the restrictions and the possibilities of the Memristive Biosensors' integration with additional elements that would allow effective readout in more complex configurations.

System reliability estimation during early design phases facilitates informed decisions for the integration of effective protection mechanisms against different classes of hardware faults. When not all system abstraction layers (technology, circuit, microarchitecture, software) are factored in such an estimation model, the delivered reliability reports must be excessively pessimistic and thus lead to unacceptably expensive, over-designed systems. We propose a scalable, cross-layer methodology and supporting suite of tools for accurate but fast estimations of computing systems reliability. The backbone of the methodology is a component-based Bayesian model, which effectively calculates system reliability based on the masking probabilities of individual hardware and software components considering their complex interactions. Our detailed experimental evaluation for different technologies, microarchitectures, and benchmarks demonstrates that the proposed model delivers very accurate reliability estimations (FIT rates) compared to statistically significant but slow fault injection campaigns at the microarchitecture level.

Nowadays, the scientific community is looking for ways to understand the effect of software execution on the reliability of a complex system when the hardware layer is unreliable. This paper proposes a statistical reliability analysis model able to estimate system reliability considering both the hardware and the software layer of a system. Bayesian Networks are employed to model hardware resources of the processor and instructions of program traces. They are exploited to investigate the probability of input errors to alter both the correct behavior and the output of the program. Experimental results show that Bayesian networks prove to be a promising model, allowing to get accurate and fast reliability estimations w.r.t. fault injection/simulation approaches.

Analyzing the impact of software execution on the reliability of a complex digital system is an increasing challenging task. Current approaches mainly rely on time consuming fault injections experiments that prevent their usage in the early stage of the design process, when fast estimations are required in order to take design decisions. To cope with these limitations, this paper proposes a statistical reliability analysis model based on Bayesian Networks. The proposed approach is able to estimate system reliability considering both the hardware and the software layer of a system, in presence of hardware transient and permanent faults. In fact, when digital system reliability is under analysis, hardware resources of the processor and instructions of program traces are employed to build a Bayesian Network. Finally, the probability of input errors to alter both the correct behavior of the system and the output of the program is computed. According to experimental results presented in this paper, it can be stated that Bayesian Network model is able to provide accurate reliability estimations in a very short period of time. As a consequence it can be a valid alternative to fault injection, especially in the early stage of the design.

Advanced multifunctional computing systems realized in forthcoming technologies hold the promise of a significant increase of the computational capability that will offer end-users ever improving services and functionalities (e.g., next generation mobile devices, cloud services, etc.). However, the same path that is leading technologies toward these remarkable achievements is also making electronic devices increasingly unreliable, posing a threat to our society that is depending on the ICT in every aspect of human activities. Reliability of electronic systems is therefore a key challenge for the whole ICT technology and must be guaranteed without penalizing or slowing down the characteristics of the final products. CLERECO EU FP7 (GA No. 611404) research project addresses early accurate reliability evaluation and efficient exploitation of reliability at different design phases, since these aspects are two of the most important and challenging tasks toward this goal.

Nowadays Field-Programmable Gate Arrays (FP-GAs) are increasingly used in critical applications. In these scenarios fault tolerance techniques are needed to increase system dependability and lifetime. This paper proposes a novel methodology to achieve autonomous fault tolerance in FPGA-based systems affected by permanent faults. A design flow is defined to help designers to build a system with increased lifetime and availability. The methodology exploits Dynamic Partial Reconfiguration (DPR) to relocate at run-time faulty modules implemented onto the FPGA. A partitioning method is also presented to provide a solution which maximizes the number of permanent faults the system can tolerate. Experimental results highlight the negligible performance degradation introduced by applying the proposed methodology, and the improvements with respect to state-of-the-art solutions.

Evaluation of computing systems reliability must be accurate enough to provide hints for the required fault protection mechanisms that will guarantee correctness of operation at acceptance costs. To be useful, reliability evaluation must be performed early enough in the design cycle when, however, the available details of the system are largely unknown. This inherent contradiction in terms: early vs. accurate, requires a cross-layer approach for reliability evaluation. Different layers of abstraction contribute differently in the overall system reliability; if this contribution can be assessed independently, the reliability of the system can be evaluated at the early stages of the design. We review the state-of-the-art in the area and discuss corresponding challenges .