Linux Looking To Make 5-Level Paging Support Unconditional For x86_64 Kernel Builds

It’s been nearly one decade since Intel began working on 5-level paging support for the Linux kernel to allow for greater virtual and physical address space with expanding memory sizes. The 5-level paging kernel-side bits were upstreamed back in Linux 4.12 in 2017 and enabled by default since 2019 with Linux 5.5. Intel CPUs for a while (since Ice Lake) have supported 5-level paging and AMD CPUs too since Zen 4. The Linux kernel may move to unconditionally enabling 5-level paging support for x86_64 kernel builds.

Intel is moving along to unconditionally enable 5-level paging support within the Linux kernel. This is about extending the virtual address size from 48 to 57 bits to allow up to 128PB of virtual memory.

This patch series sent out recently by Intel engineer Kirill Shutemov aims to remove the “CONFIG_X86_5LEVEL” Kconfig build-time option and simply have 5-level paging always enabled for new x86_64 kernel builds.

“Both Intel and AMD CPUs support 5-level paging, which is expected to become more widely adopted in the future.

Remove CONFIG_X86_5LEVEL.

In preparation to that remove CONFIG_DYNAMIC_MEMORY_LAYOUT and make SPARSEMEM_VMEMMAP the only memory model.”

In practice this doesn’t mean a whole lot with most Linux distribution vendor kernels shipping with CONFIG_X86_5LEVEL enabled, but it’s one less knob and a sign of the times with catering more of the upstream kernel to modern hardware needs.