PR Crisis: Analyzing and Fixing Partial Reconfiguration in Multi-Tenant Cloud FPGAs.

FPGAs are increasingly being used in cloud systems, mainly due to their performance and energy advantages. Recent FPGAs have a relatively large amount of resources, which enables multi-tenancy and hence improves the utilization and economic value for both the cloud providers and customers. However, the ability to co-locate designs from different tenants requires efficient safeguards and support. Fortunately, the majority of the recent FPGAs, e.g., those from Xilinx (currently AMD), include partial reconfiguration (PR) capabilities which enable partitioning and independently programming the FPGA resources. FPGA's PR capability is considered vital for the temporal and spatial sharing of FPGAs in cloud environments. In this work, we systematically study how the various power profiles for FPGA partitions can impact the process of programming partitions and the overall functionality of the FPGA. Surprisingly, we observe that high power activity in partitions can significantly impact the programming time of other partitions. Even worse, we observe that carefully crafted power viruses can delay (or even) fail the whole PR process, and in some cases cause the shutting down of the whole FPGA. Accordingly, we describe such attacks in detail and discuss how they can impact the availability and timeliness (in the case of real-time workloads) of multi-tenant FPGAs. Finally, we propose a lightweight solution that can effectively detect such abnormal power activities and hence blocks any channels for such attacks before the PR process starts.