Linux 6.10 On RISC-V Allows Configurable Boot Image Compression

A few days ago with the main RISC-V architecture pull for Linux 6.10 was enabling Rust support within the kernel for this ISA as well as other additions. A secondary set of RISC-V changes have been merged as well ahead of the Linux 6.10 merge window closing this weekend.

With this second set of RISC-V changes for Linux 6.10 are some performance optimizations, bug fixes and clean-ups, and then most notable is allowing changing the compression format for the kernel boot images.

Up to this point the RISC-V Linux kernel build image would be uncompressed unless the execute in place (XIP_KERNEL) or EFI_ZBOOT options were enabled. If going the latter route, a GZ image would be unconditionally used. But now on Linux 6.10 is the option of selecting between BZ2, LZ4, LZMA, LZO, and Zstd compression formats as well for the boot image.

So moving forward those spinning their own RISC-V kernel builds can make use of the CONFIG_KERNEL_ZSTD, CONFIG_KERNEL_LZ4, and similar compression Kconfig options for selecting their desired compression algorithm for the kernel image.

That configurable compression format for the RISC-V boot kernel images landed in upstream Linux 6.10 via this pull. The other major CPU architectures have already allowed this configurable compression support.