Glossary
KPTI (kernel page-table isolation)
A Linux mitigation that gives user and kernel modes separate page tables, unmapping the kernel while userspace runs; introduced to mitigate Meltdown.
KPTI (Kernel Page-Table Isolation) gives user mode and kernel mode separate page tables. While a process runs in user mode, almost none of the kernel is mapped into its address space; a small trampoline switches to the full kernel page table on entry and back on exit.
KPTI was introduced to mitigate Meltdown, a speculative-execution side channel that let user space read kernel memory. As a side effect it also removes some of the address-space sharing that older kernel exploits relied on, though it is not a general anti-ROP control. It is a core part of a modern kernel's isolation posture alongside KASLR and SMEP/SMAP. See KASLR, KPTI and modern kernel defenses.