Speculative side channel attack mitigation using uncacheable memory

• Main Authors: Johnson, Kenneth D, Kishan, Arun Upadhyaya, Ramachandran, Sai Ganesh, Hepkin, David Alan, Zhang, Xin David
• Format: Patent
• Language: English
• Published: 14.04.2020
• Subjects: CALCULATING; COMPUTING; COUNTING; ELECTRIC DIGITAL DATA PROCESSING; PHYSICS

Speculative side channels exist when memory is accessed by speculatively-executed processor instructions. Embodiments use uncacheable memory mappings to close speculative side channels that could allow an unprivileged execution context to access a privileged execution context's memory. Based on allocation of memory location(s) to the unprivileged execution context, embodiments map these memory location(s) as uncacheable within first page table(s) corresponding to the privileged execution context, but map those same memory locations as cacheable within second page table(s) corresponding to the unprivileged execution context. This prevents a processor from carrying out speculative execution of instruction(s) from the privileged execution context that access any of this memory allocated to the unprivileged execution context, due to the unprivileged execution context's memory being mapped as uncacheable for the privileged execution context. Performance for the unprivileged execution context is substantially unaffected, however, since this memory is mapped as cacheable for the unprivileged execution context.