When user and kernel mode processes are scheduled to run simultaneously on the same physical processor core via simultaneous multithreading, processor vulnerabilities can result in sensitive data restricted to kernel-mode processes being leaked to user-mode processes. While disabling simultaneous multithreading or use of a scheduler that determines sequence of execution can prevent such leakage, these changes degrade processor performance. This disclosure describes the use of per-CPU counters to track when each physical core of a processor begins and ends the execution of a program thread running in the kernel mode. Upon detection of such a thread, the core is identified as being in an unsafe state and all user-mode tasks are halted using an inter-processor interrupt.
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Fernandes, Joel Agnel, "Use of Per-CPU Counters to Protect Kernel-Mode Processes on a Multicore Processor", Technical Disclosure Commons, (December 01, 2020)