The Spectre Mitigation Impact For Intel Ice Lake With Core i7-1065G7
For those wondering if -- or how much -- of a performance impact mitigations still make regarding Spectre for Intel's long-awaited 10nm+ Ice Lake processors, here is the rundown on the mitigation state and the performance impact.
One of the areas that Phoronix readers have requested testing on with the recent purchase of the Dell XPS 7390 with Core i7 1065G7 is regarding the mitigation state and performance. Ice Lake with its Sunny Cove microarchitecture -- similar to Cascade Lake -- is no longer affected by Meltdown, MDS, or L1TF / Foreshadow.
On Ice Lake for Spectre V4 "Speculative Store Bypass" is the standard Linux mitigations for SSD via prctl and SECCOMP interfaces is still applied, Spectre V1 mitigations are usercopy and SWAPGS barriers and __user pointer sanitization, and Spectre V2 mitigations of enhanced IBRS (Indirect Branch Restricted Speculation) IBPB (Indirect Branch Predictor Barrier) and conditional RSB (Return Stack Buffer) filling. Those are the default mitigations found for the Ice Lake Core i7-1065G7 when running on Ubuntu 19.10 with the Linux 5.3 kernel.
Booting the Linux kernel with the "mitigations=off" argument allows disabling those software mitigations still relevant for Ice Lake processors.
So from the Dell XPS 7390 running Ubuntu 19.10, I ran benchmarks out-of-the-box/default with the mitigations and then again after booting the Linux 5.3 kernel with the mitigations disabled. Via the Phoronix Test Suite a wide variety of workloads were tested for seeing the impact on performance for Ice Lake of those mitigations.