A whole class of speculative execution attacks against CPUs were published in 2018. They seemed pretty catastrophic at the time. But the fixes were as well. Speculative execution was a way to speed up CPUs, and removing those enhancements resulted in significant performance drops.

Now, people are rethinking the trade-off. Ubuntu has disabled some protections, resulting in 20% performance boost.

After discussion between Intel and Canonical’s security teams, we are in agreement that Spectre no longer needs to be mitigated for the GPU at the Compute Runtime level. At this point, Spectre has been mitigated in the kernel, and a clear warning from the Compute Runtime build serves as a notification for those running modified kernels without those patches. For these reasons, we feel that Spectre mitigations in Compute Runtime no longer offer enough security impact to justify the current performance tradeoff.

I agree with this trade-off. These attacks are hard to get working, and it’s not easy to exfiltrate useful data. There are way easier ways to attack systems.

News article.