Intel CPUs Witness Downfall In Performance After “Downfall” Vulnerability Mitigations Applied

The Downfall vulnerability was recently reported to have compromised several Intel CPUs leading to serious security backdoor implications and the mitigations were expected to have performance impacts. Phoronix has now published benchmarks of the vulnerability's mitigation, demonstrating the effects of "Downfall."

While we have put up a detailed report on Intel's Downfall vulnerability, for a quick recap, the vulnerability specifically affects workloads utilizing the AVX2/AVX-512 gather instructions. Intel disclosed that "Downfall" had a greater impact on older-gen Tiger Lake/ Ice Lake lineups. In easy words, the vulnerability reveals hardware registry contents, potentially leading to large-scale data thefts.

To solve the issue, Intel released microcode mitigation, which brought in performance impacts on a large level. Initially, the effects of mitigation were unknown. However, Phoronix went out of the way and tested the impacted CPUs to give an idea of how detrimental the vulnerability is. They test Intel's Xeon Platinum 8380, Xeon Gold 6226R, and the Core i7-1165G7. All three processors were exposed to the vulnerability; hence if you want to know whether your CPU is impacted, you can view the complete list provided by Intel.

Moving on to the benchmarks, the Xeon Platinum 8380 was observed in various instances, with the old "390" and the new "3a5" microcodes. As predicted, the processor saw a performance decline in all scenarios. In OpenVKL, the performance drop was recorded at 6%, while in OSPRay 1.2, it reached 34%. AI workloads oversaw a vast drop, with applications such as Neural Magic DeepSparse 1.5, which was expected given that the HPC workloads were predicted to drop.

Coming to the Intel Xeon Gold 6226R CPUs, as expected, also witnessed a performance hit reaching around 9% in OpenVKL, while seeing a more considerable 33% reduction in OSPRay 1.2. The impacts were on all benchmarks tested, showing that the vulnerability had its grasp over several Intel processors.

The more consumer-focused Intel Core i7-1165G7 CPU couldn't prevent the mitigation from affecting its performance, as the processors took massive hits. The performance penalties were similar to those of the other processors tested, varying from 19-39% in OSPRay 2.12, while it showed an almost 11% reduction in OpenVLK 1.3.1. The "Downfall" vulnerability compromised multiple processors, even impacting the mainstream ones, such as the Alder Lake CPUs.

In all this mess, a good thing that comes out is that the performance decline was nowhere close to the initially predicted 50% by Intel themselves, and the results showed that the drops were actually not that intense.

However, the benchmarks demonstrated a significant decline even after this, which must be addressed here. As previously said, the testing by Phoronix reveals that HPC workloads took the more significant hit, and we believe "Downfall" isn't something to worry about for an average consumer confined to gaming and entertainment.

Intel previously said to "disable" the CPU microcode if you don't want the performance penalties. However, it could lead to greater risk, especially for corporations, since data leakage is a significant tradeoff. While chances of the attack are low here, having your security at compromise is something we would never suggest.

News Source: Phoronix