Linux 6.12 Patches Neoverse-N3 & Microsoft Azure Cobalt 100 For Speculative SSBS

Written by Michael Larabel in Arm on 5 October 2024 at 08:53 AM EDT. Add A Comment
ARM
We are not done yet seeing new Arm cores still impacted by the Speculative Store Bypass handling errata. Merged to Linux 6.12 on Friday was adding the speculative SSBS workaround for the Cortex-A715, Neoverse-N3, and Microsoft Azure Cobalt 100 cores.

Over the past few months we have seen more Arm CPU cores needing the speculative SBBS workaround. The issue deals with MSR writes to the SSBS (Speculative Store Bypass Safe) special purpose register not affecting subsequent speculative instructions. This issue when unmitigated can lead to speculative store bypassing for a period of time.

Microsoft Cobalt 100 CPU


The workaround within the Linux kernel adds a speculation barrier after MSR writes to the SSBS register. A variety of Cortex and Neoverse cores to date have needed this workaround while the list has grown longer as of Friday. The Cortex-A715, Neoverse-N3, and Microsoft Azure Cobalt 100 are the latest where this workaround/mitigation is being applied.

This went into effect via this merge to Linux 6.12 Git on Friday and will be found in Sunday's Linux 6.12-rc2 kernel.
Related News
About The Author
Michael Larabel

Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via MichaelLarabel.com.

Popular News This Week