Hi Pavel, After going through this series, I think if this can be done by using identity map through ttbr0. Then the processes may be neat (I hope so): -1. set up identity map in machine_kexec_post_load(), instead of copying linear map. -2. Also past this temporary identity map to arm64_relocate_new_kernel() -3. in arm64_relocate_new_kernel(), just load identity map and re-enable MMU. After copying, just turn off MMU. Thanks, Pingfan On Thu, Mar 4, 2021 at 3:47 PM Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> wrote: > > Changelog: > v12: > - A major change compared to previous version. Instead of using > contiguous VA range a copy of linear map is now used to perform > copying of segments during relocation as it was agreed in the > discussion of version 11 of this project. > - In addition to using linear map, I also took several ideas from > James Morse to better organize the kexec relocation: > 1. skip relocation function entirely if that is not needed > 2. remove the PoC flushing function since it is not needed > anymore with MMU enabled. > v11: > - Fixed missing KEXEC_CORE dependency for trans_pgd.c > - Removed useless "if(rc) return rc" statement (thank you Tyler Hicks) > - Another 12 patches were accepted into maintainer's get. > Re-based patches against: > https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git > Branch: for-next/kexec > v10: > - Addressed a lot of comments form James Morse and from Marc Zyngier > - Added review-by's > - Synchronized with mainline > > v9: - 9 patches from previous series landed in upstream, so now series > is smaller > - Added two patches from James Morse to address idmap issues for machines > with high physical addresses. > - Addressed comments from Selin Dag about compiling issues. He also tested > my series and got similar performance results: ~60 ms instead of ~580 ms > with an initramfs size of ~120MB. > v8: > - Synced with mainline to keep series up-to-date > v7: > -- Addressed comments from James Morse > - arm64: hibernate: pass the allocated pgdp to ttbr0 > Removed "Fixes" tag, and added Added Reviewed-by: James Morse > - arm64: hibernate: check pgd table allocation > Sent out as a standalone patch so it can be sent to stable > Series applies on mainline + this patch > - arm64: hibernate: add trans_pgd public functions > Remove second allocation of tmp_pg_dir in swsusp_arch_resume > Added Reviewed-by: James Morse <james.morse@xxxxxxx> > - arm64: kexec: move relocation function setup and clean up > Fixed typo in commit log > Changed kern_reloc to phys_addr_t types. > Added explanation why kern_reloc is needed. > Split into four patches: > arm64: kexec: make dtb_mem always enabled > arm64: kexec: remove unnecessary debug prints > arm64: kexec: call kexec_image_info only once > arm64: kexec: move relocation function setup > - arm64: kexec: add expandable argument to relocation function > Changed types of new arguments from unsigned long to phys_addr_t. > Changed offset prefix to KEXEC_* > Split into four patches: > arm64: kexec: cpu_soft_restart change argument types > arm64: kexec: arm64_relocate_new_kernel clean-ups > arm64: kexec: arm64_relocate_new_kernel don't use x0 as temp > arm64: kexec: add expandable argument to relocation function > - arm64: kexec: configure trans_pgd page table for kexec > Added invalid entries into EL2 vector table > Removed KEXEC_EL2_VECTOR_TABLE_SIZE and KEXEC_EL2_VECTOR_TABLE_OFFSET > Copy relocation functions and table into separate pages > Changed types in kern_reloc_arg. > Split into three patches: > arm64: kexec: offset for relocation function > arm64: kexec: kexec EL2 vectors > arm64: kexec: configure trans_pgd page table for kexec > - arm64: kexec: enable MMU during kexec relocation > Split into two patches: > arm64: kexec: enable MMU during kexec relocation > arm64: kexec: remove head from relocation argument > v6: > - Sync with mainline tip > - Added Acked's from Dave Young > v5: > - Addressed comments from Matthias Brugger: added review-by's, improved > comments, and made cleanups to swsusp_arch_resume() in addition to > create_safe_exec_page(). > - Synced with mainline tip. > v4: > - Addressed comments from James Morse. > - Split "check pgd table allocation" into two patches, and moved to > the beginning of series for simpler backport of the fixes. > Added "Fixes:" tags to commit logs. > - Changed "arm64, hibernate:" to "arm64: hibernate:" > - Added Reviewed-by's > - Moved "add PUD_SECT_RDONLY" earlier in series to be with other > clean-ups > - Added "Derived from:" to arch/arm64/mm/trans_pgd.c > - Removed "flags" from trans_info > - Changed .trans_alloc_page assumption to return zeroed page. > - Simplify changes to trans_pgd_map_page(), by keeping the old > code. > - Simplify changes to trans_pgd_create_copy, by keeping the old > code. > - Removed: "add trans_pgd_create_empty" > - replace init_mm with NULL, and keep using non "__" version of > populate functions. > 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 > ----------------------------------- > v11: https://lore.kernel.org/lkml/20210127172706.617195-1-pasha.tatashin@xxxxxxxxxx > v10: https://lore.kernel.org/linux-arm-kernel/20210125191923.1060122-1-pasha.tatashin@xxxxxxxxxx > v9: https://lore.kernel.org/lkml/20200326032420.27220-1-pasha.tatashin@xxxxxxxxxx > v8: https://lore.kernel.org/lkml/20191204155938.2279686-1-pasha.tatashin@xxxxxxxxxx > v7: https://lore.kernel.org/lkml/20191016200034.1342308-1-pasha.tatashin@xxxxxxxxxx > v6: https://lore.kernel.org/lkml/20191004185234.31471-1-pasha.tatashin@xxxxxxxxxx > v5: https://lore.kernel.org/lkml/20190923203427.294286-1-pasha.tatashin@xxxxxxxxxx > v4: https://lore.kernel.org/lkml/20190909181221.309510-1-pasha.tatashin@xxxxxxxxxx > v3: https://lore.kernel.org/lkml/20190821183204.23576-1-pasha.tatashin@xxxxxxxxxx > v2: https://lore.kernel.org/lkml/20190817024629.26611-1-pasha.tatashin@xxxxxxxxxx > v1: https://lore.kernel.org/lkml/20190801152439.11363-1-pasha.tatashin@xxxxxxxxxx > > James Morse (4): > arm64: hyp-stub: Check the size of the HYP stub's vectors > arm64: hyp-stub: Move invalid vector entries into the vectors > arm64: hyp-stub: Move el1_sync into the vectors > arm64: kexec: Use dcache ops macros instead of open-coding > > Pavel Tatashin (13): > arm64: kernel: add helper for booted at EL2 and not VHE > arm64: trans_pgd: hibernate: Add trans_pgd_copy_el2_vectors > arm64: hibernate: abstract ttrb0 setup function > arm64: kexec: flush image and lists during kexec load time > arm64: kexec: skip relocation code for inplace kexec > arm64: kexec: pass kimage as the only argument to relocation function > arm64: kexec: kexec may require EL2 vectors > arm64: kexec: relocate in EL1 mode > arm64: kexec: use ld script for relocation function > arm64: kexec: install a copy of the linear-map > arm64: kexec: keep MMU enabled during kexec relocation > arm64: kexec: remove the pre-kexec PoC maintenance > arm64: kexec: Remove cpu-reset.h > > arch/arm64/Kconfig | 2 +- > arch/arm64/include/asm/assembler.h | 31 ++++- > arch/arm64/include/asm/kexec.h | 12 ++ > arch/arm64/include/asm/mmu_context.h | 24 ++++ > arch/arm64/include/asm/sections.h | 1 + > arch/arm64/include/asm/trans_pgd.h | 3 + > arch/arm64/include/asm/virt.h | 8 ++ > arch/arm64/kernel/asm-offsets.c | 11 ++ > arch/arm64/kernel/cpu-reset.S | 7 +- > arch/arm64/kernel/cpu-reset.h | 32 ----- > arch/arm64/kernel/hibernate-asm.S | 20 ---- > arch/arm64/kernel/hibernate.c | 56 +++------ > arch/arm64/kernel/hyp-stub.S | 95 +++++++-------- > arch/arm64/kernel/machine_kexec.c | 168 +++++++++++++++------------ > arch/arm64/kernel/relocate_kernel.S | 72 ++++++------ > arch/arm64/kernel/sdei.c | 2 +- > arch/arm64/kernel/vmlinux.lds.S | 19 +++ > arch/arm64/mm/trans_pgd.c | 20 ++++ > 18 files changed, 314 insertions(+), 269 deletions(-) > delete mode 100644 arch/arm64/kernel/cpu-reset.h > > -- > 2.25.1 > _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
