tlbi= Boot Option Submitted Ahead Of Linux 7.2 Kernel Release

Ahead of the Linux 7.2 kernel stable release expected to occur in the coming hours, a last minute "x86/urgent" pull request was submitted with one patch for adding the new tlbi= boot option. The new tlbi= option has been submitted in time for Linux 7.2 stable and also marked for back-porting to stable Linux kernel versions. This option controls the TLB invalidation method and tlbi=ipi is the only option currently honored. Booting the kernel with tlbi=ipi will switch back to IPI-based Transparent Lookaside Buffer (TLB) flushing. Due to some recently discovered INVLPGB / TLBSYNC issues on AMD CPUs with INVLPGB used for broadcast TLB flushing on recent kernel versions, this option is added to allow developers/administrators to switch back to the old IPI-based TLB flushing in order to rule it out as a potential cause of user-space crashes. Thus for now this is just a debug option if wanting to rule out any INVLPGB/TLBSYNC issues on your Linux system. In the future it's mentioned it may be extended to support tlbi=broadcast should the current default behavior change. The patch is pending via the x86/urgent pull request and should be mainlined to the Linux kernel shortly.