Linux Returns To Parallel CPU Microcode Updates To Reduce Cloud Disruption

Written by Michael Larabel in Hardware on 4 October 2019 at 07:12 AM EDT. 11 Comments
Following the Spectre mitigations coming to light last year, the late microcode update process for CPUs was serialized. However, this has led to complaints from cloud vendors and other customers with large core count servers where downtime/disruptions need to be minimal. So now the CPU microcode update process is being parallelized again.

Serial late microcode updates on large core count servers was slow with it being done one CPU at a time. In the change by an Intel engineer, he acknowledged "cloud customers have expressed discontent." So now it's being parallelized again while ensuring only one core is updated at a time, i.e. not the SMT sibling thread.

At least one of the cloud vendors seeking this serial/parallel CPU microcode change was Oracle. That change is now queued in tip.git as material waiting around until Linux 5.5 unless some urgency is determined to get it into 5.4 as a "fix" for the kernel.
Related News
About The Author
Michael Larabel

Michael Larabel is the principal author of 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 automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via

Popular News This Week