AMD recently disclosed a newly-surfaced "Inception" CPU vulnerability without revealing any information about the performance effects when mitigation is applied. However, Phoronix has tested out the results of the new microcode, portraying significant performance downgrades.
AMD's Latest "Inception" Vulnerability Leads to Significant Performance Hits, However Limited to Certain Applications
For those unaware of the vulnerability, we recently discussed it in detail; however, for a quick recap, Inception aims to misguide your processor by creating an instruction that leads a CPU into a repeating function. This can lead to a potential data leak and be disastrous for organizations with "sensitive data." Moreover, the vulnerability expands to all Zen CPUs, which creates an alarming situation for consumers on the AMD platform.
You will be disappointed to hear that AMD hasn't released a mitigation yet; however, as Phoronix states, kernel-based mitigation does the job for Zen 1 & Zen 2 CPUs, whereas Zen 3 and Zen 4 users might need to wait here. However, AMD has released a mitigated microcode for "Family 19h" processors, which are EPYC processors. Phoronix has obtained benchmarks by utilizing the microcode on AMD's EPYC 7763, and the results are indeed interesting.
Before diving into benchmarks, you will see the multiple results obtained under "safe RET" and others. To clarify, these are tiers of "mitigations" released by AMD, some of which are "kernel-based" while the others are entirely on the newly released microcode, due to which performance varies.
While we won't dive into factual data since that makes things complicated to interpret, we will summarize it. Phoronix performed extensive tests, especially in popular applications like Blender and Mozilla Firefox. The results reveal that the new "mitigation" has little to no impact on user applications. The greatest fall was seen in 7zip compression, which witnessed an almost -13% drop in performance. This concludes that the average consumer shouldn't worry about applying the mitigation.
However, significant drops were seen in more "intensive" applications such as MariaDB. The performance tradeoff exceeded the 50% mark, revealing that the microcode severely impacts applications based on data processing.
Popping up new vulnerabilities is a norm in the industry, as is the performance drop with its mitigation. A prime example is the recent Intel "Downfall," which brought get in performance drops above 50%. We hope the vulnerabilities are addressed quickly since they can prove to be fatal in case a fix is prolonged.
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