An engineer from VMware brought to the attention of the Linux kernel developer community a significant drop in performance when using the Linux kernel 5.19. Testing a virtual machine with the 5.19 kernel in a VMware ESXi hypervisor environment showed a 70% decrease in computational performance, a 30% decrease in network operations, and a 13% decrease in storage actions, compared to the same configuration based on kernel 5.18.
The reason for the performance decline is attributed to a change in the protection code against Spectre v2 class attacks (spectre_v2=ibrs), implemented based on Enhanced Indirect Branch Restricted Speculation (IBRS), which allows adaptive enabling and disabling of speculative execution of instructions during interrupt handling, system calls, and context switching. This protection is enabled to block the newly discovered Retbleed vulnerability in the speculative execution mechanism of indirect CPU branches, which can extract information from kernel memory or launch an attack on the host system from of virtual machines. After disabling the protection (spectre_v2=off), performance returns to its previous level.
Source: opennet.ru
