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Message-ID: <YTh7cFoduzQwRwxk@piliu.users.ipa.redhat.com>
Date: Wed, 8 Sep 2021 16:59:28 +0800
From: Pingfan Liu <piliu@...hat.com>
To: Pavel Tatashin <pasha.tatashin@...een.com>
Cc: jmorris@...ei.org, sashal@...nel.org, ebiederm@...ssion.com,
kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
corbet@....net, catalin.marinas@....com, will@...nel.org,
linux-arm-kernel@...ts.infradead.org, maz@...nel.org,
james.morse@....com, vladimir.murzin@....com,
matthias.bgg@...il.com, linux-mm@...ck.org, mark.rutland@....com,
steve.capper@....com, rfontana@...hat.com, tglx@...utronix.de,
selindag@...il.com, tyhicks@...ux.microsoft.com,
kernelfans@...il.com, akpm@...ux-foundation.org,
madvenka@...ux.microsoft.com
Subject: Re: [PATCH v16 00/15] arm64: MMU enabled kexec relocation
On Mon, Aug 02, 2021 at 05:53:53PM -0400, Pavel Tatashin wrote:
> Changelog:
> v16:
> - Merged with 5.14-rc4
> v15:
> - Changed trans_pgd_copy_el2_vectors() to use vector table that
> only shared by kexec and hibernate. This way sync does not have
> dangling branch that was recently introduced. (Reported by Marc
> Zyngier)
> - Renamed is_hyp_callable() to is_hyp_nvhe() as requested by Marc
> Zyngier
> - Clean-ups, comment fixes.
> - Sync with upstream 368094df48e680fa51cedb68537408cfa64b788e
> v14:
> - Fixed a bug in "arm64: hyp-stub: Move elx_sync into the vectors"
> that was noticed by Marc Zyngier
> - Merged with upstream
> v13:
> - Fixed a hang on ThunderX2, thank you Pingfan Liu for reporting
> the problem. In relocation function we need civac not ivac, we
> need to clean data in addition to invalidating it.
> Since I was using ThunderX2 machine I also measured the new
> performance data on this large ARM64 server. The MMU improves
> kexec relocation 190 times on this machine! (see below for
> raw data). Saves 7.5s during CentOS kexec reboot.
> 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@....com>
> - 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
> ----------------
>
> Cavium ThunderX2:
> Kernel Image size: 38M Iniramfs size: 46M Total relocation size: 84M
> MMU-disabled:
> relocation 7.489539915s
> MMU-enabled:
> relocation 0.03946095s
>
> Relocation performance is improved 190 times.
>
> Broadcom Stingray:
> 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.
>
> MMU-disabled::
> kernel shutdown 0.022131328s
> relocation 0.440510736s
> kernel startup 0.294706768s
>
> Relocation was taking: 58.2% of reboot time
>
> MMU-enabled:
> 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
> -----------------------------------
> v15: https://lore.kernel.org/lkml/20210609004419.936873-1-pasha.tatashin@soleen.com
> v14: https://lore.kernel.org/lkml/20210527150526.271941-1-pasha.tatashin@soleen.com
> v13: https://lore.kernel.org/lkml/20210408040537.2703241-1-pasha.tatashin@soleen.com
> v12: https://lore.kernel.org/lkml/20210303002230.1083176-1-pasha.tatashin@soleen.com
> v11: https://lore.kernel.org/lkml/20210127172706.617195-1-pasha.tatashin@soleen.com
> v10: https://lore.kernel.org/linux-arm-kernel/20210125191923.1060122-1-pasha.tatashin@soleen.com
> v9: https://lore.kernel.org/lkml/20200326032420.27220-1-pasha.tatashin@soleen.com
> v8: https://lore.kernel.org/lkml/20191204155938.2279686-1-pasha.tatashin@soleen.com
> v7: https://lore.kernel.org/lkml/20191016200034.1342308-1-pasha.tatashin@soleen.com
> v6: https://lore.kernel.org/lkml/20191004185234.31471-1-pasha.tatashin@soleen.com
> v5: https://lore.kernel.org/lkml/20190923203427.294286-1-pasha.tatashin@soleen.com
> v4: https://lore.kernel.org/lkml/20190909181221.309510-1-pasha.tatashin@soleen.com
> v3: https://lore.kernel.org/lkml/20190821183204.23576-1-pasha.tatashin@soleen.com
> v2: https://lore.kernel.org/lkml/20190817024629.26611-1-pasha.tatashin@soleen.com
> v1: https://lore.kernel.org/lkml/20190801152439.11363-1-pasha.tatashin@soleen.com
>
> Pavel Tatashin (15):
> 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: Use dcache ops macros instead of open-coding
> arm64: kexec: pass kimage as the only argument to relocation function
> arm64: kexec: configure EL2 vectors for kexec
> 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
> arm64: trans_pgd: remove trans_pgd_map_page()
>
> arch/arm64/Kconfig | 2 +-
> arch/arm64/include/asm/assembler.h | 49 ++++++--
> 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 | 12 +-
> arch/arm64/include/asm/virt.h | 7 ++
> 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 | 72 -----------
> arch/arm64/kernel/hibernate.c | 49 ++------
> arch/arm64/kernel/machine_kexec.c | 177 ++++++++++++++-------------
> arch/arm64/kernel/relocate_kernel.S | 70 +++++------
> arch/arm64/kernel/sdei.c | 2 +-
> arch/arm64/kernel/vmlinux.lds.S | 19 +++
> arch/arm64/mm/Makefile | 1 +
> arch/arm64/mm/trans_pgd-asm.S | 65 ++++++++++
> arch/arm64/mm/trans_pgd.c | 82 ++++---------
> 19 files changed, 356 insertions(+), 338 deletions(-)
> delete mode 100644 arch/arm64/kernel/cpu-reset.h
> create mode 100644 arch/arm64/mm/trans_pgd-asm.S
>
>
> base-commit: c500bee1c5b2f1d59b1081ac879d73268ab0ff17
> --
Tested-by: Pingfan Liu <piliu@...hat.com>
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