Preface: A Memory Management Unit (MMU) is the hardware system which performs both virtual memory mapping and checks the current privilege to keep user processes separated from the operating system — and each other. In addition it helps to prevent caching of ‘volatile’ memory regions (such as areas containing I/O peripherals.

Background: Generally speaking, GPU firmware and driver functionality do utilize the L2 cache. The L2 cache in a GPU is a larger, shared cache that helps improve memory access speeds and reduce latency for various operations. It plays a crucial role in optimizing the performance of GPU-accelerated tasks by storing frequently accessed data closer to the GPU cores.

The L2 cache is particularly important for managing memory access across different Streaming Multiprocessors (SMs) within the GPU. By efficiently handling memory requests and reducing the need for crossbar communication, the L2 cache helps minimize latency and improve overall task performance.

Vulnerability details: Kernel software installed and running inside a Guest VM may exploit memory shared with the GPU Firmware to write data into another Guest’s virtualised GPU memory.

Official announcement: Please refer to the vendor announcement for details – https://nvd.nist.gov/vuln/detail/CVE-2024-46975