Changelog: v3: - Split changes to create_safe_exec_page() into several patches for easier review as request by Mark Rutland. This is why this series has 3 more patches. - Renamed trans_table to tans_pgd as agreed with Mark. The header comment in trans_pgd.c explains that trans stands for transitional page tables. Meaning they are used in transition between two kernels. v2: - Fixed hibernate bug reported by James Morse - Addressed comments from James Morse: * More incremental changes to trans_table * Removed TRANS_FORCEMAP * Added kexec reboot data for image with 380M in size. Enable MMU during kexec relocation in order to improve reboot performance. If kexec functionality is used for a fast system update, with a minimal downtime, the relocation of kernel + initramfs takes a significant portion of reboot. The reason for slow relocation is because it is done without MMU, and thus not benefiting from D-Cache. Performance data ---------------- For this experiment, the size of kernel plus initramfs is small, only 25M. If initramfs was larger, than the improvements would be greater, as time spent in relocation is proportional to the size of relocation. Previously: kernel shutdown 0.022131328s relocation 0.440510736s kernel startup 0.294706768s Relocation was taking: 58.2% of reboot time Now: kernel shutdown 0.032066576s relocation 0.022158152s kernel startup 0.296055880s Now: Relocation takes 6.3% of reboot time Total reboot is x2.16 times faster. With bigger userland (fitImage 380M), the reboot time is improved by 3.57s, and is reduced from 3.9s down to 0.33s Previous approaches and discussions ----------------------------------- https://lore.kernel.org/lkml/20190817024629.26611-1-pasha.tatashin@xxxxxxxxxx version 2 of this series https://lore.kernel.org/lkml/20190801152439.11363-1-pasha.tatashin@xxxxxxxxxx version 1 of this series https://lore.kernel.org/lkml/20190709182014.16052-1-pasha.tatashin@xxxxxxxxxx reserve space for kexec to avoid relocation, involves changes to generic code to optimize a problem that exists on arm64 only: https://lore.kernel.org/lkml/20190716165641.6990-1-pasha.tatashin@xxxxxxxxxx The first attempt to enable MMU, some bugs that prevented performance improvement. The page tables unnecessary configured idmap for the whole physical space. https://lore.kernel.org/lkml/20190731153857.4045-1-pasha.tatashin@xxxxxxxxxx No linear copy, bug with EL2 reboots. Pavel Tatashin (17): kexec: quiet down kexec reboot arm64, hibernate: use get_safe_page directly arm64, hibernate: remove gotos in create_safe_exec_page arm64, hibernate: rename dst to page in create_safe_exec_page arm64, hibernate: check pgd table allocation arm64, hibernate: add trans_pgd public functions arm64, hibernate: move page handling function to new trans_pgd.c arm64, trans_pgd: make trans_pgd_map_page generic arm64, trans_pgd: add trans_pgd_create_empty arm64, trans_pgd: adjust trans_pgd_create_copy interface arm64, trans_pgd: add PUD_SECT_RDONLY arm64, trans_pgd: complete generalization of trans_pgds kexec: add machine_kexec_post_load() arm64, kexec: move relocation function setup and clean up arm64, kexec: add expandable argument to relocation function arm64, kexec: configure trans_pgd page table for kexec arm64, kexec: enable MMU during kexec relocation arch/arm64/Kconfig | 4 + arch/arm64/include/asm/kexec.h | 51 ++++- arch/arm64/include/asm/pgtable-hwdef.h | 1 + arch/arm64/include/asm/trans_pgd.h | 63 ++++++ arch/arm64/kernel/asm-offsets.c | 14 ++ arch/arm64/kernel/cpu-reset.S | 4 +- arch/arm64/kernel/cpu-reset.h | 8 +- arch/arm64/kernel/hibernate.c | 261 ++++++------------------ arch/arm64/kernel/machine_kexec.c | 199 ++++++++++++++---- arch/arm64/kernel/relocate_kernel.S | 196 +++++++++--------- arch/arm64/mm/Makefile | 1 + arch/arm64/mm/trans_pgd.c | 270 +++++++++++++++++++++++++ kernel/kexec.c | 4 + kernel/kexec_core.c | 8 +- kernel/kexec_file.c | 4 + kernel/kexec_internal.h | 2 + 16 files changed, 750 insertions(+), 340 deletions(-) create mode 100644 arch/arm64/include/asm/trans_pgd.h create mode 100644 arch/arm64/mm/trans_pgd.c -- 2.23.0
