ARM64 To Finally Broadcast Its Spectre State Via Sysfs, Prep For Neoverse & SVE2
Among the changes for ARM64 worth pointing out with this next version of the Linux kernel are:
- ARM64 will finally display the state of any Meltdown/Spectre mitigations via sysfs, matching what x86/x86_64 and other architectures have been doing since last year... Now it will be much more convenient on Linux 5.2+ for seeing what CPU vulnerability mitigations are relevant/active or not on the particular 64-bit ARM hardware. Showing up with Linux 5.2 on ARM64 is Meltdown, Spectre V2, and Speculative Store Bypass (SSB).
- Related to the sysfs mitigations broadcast, ARM64 is also supporting the new "mitigations=" kernel parameter for easily toggling/disabling these mitigations. Users can boot with "mitigations=off" for disabling the relevant CPU vulnerability mitigations that does put your system at greater risk but avoids the sometimes costly performance hits.
- Support for the recently announced Scalable Vector Extension 2 "SVE2" is exposed to user-space. SVE2 builds on SVE to offer greater SIMD vector performance and also offer new auto-vectorization techniques.
- A CPU timer erratum workaround is applied for forthcoming Neoverse N1 processors.
More details on the ARM64 changes for Linux 5.2 via this pull request.