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Message-ID: <de4c557a-c592-d9f7-d516-bc746d153fa1@oracle.com>
Date: Mon, 12 Jun 2023 12:32:27 -0500
From: Eric DeVolder <eric.devolder@...cle.com>
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Subject: Re: [PATCH v1 00/21] refactor Kconfig to consolidate KEXEC and CRASH
options
My apologies, but this patch series is 13 patches, not 21. The last patch is "PATCH v1 13/21
sh/kexec: refactor for kernel/Kconfig.kexec"
I'll correct for v2.
eric
On 6/12/23 12:27, Eric DeVolder wrote:
> The Kconfig is refactored to consolidate KEXEC and CRASH options from
> various arch/<arch>/Kconfig files into new file kernel/Kconfig.kexec.
>
> The Kconfig.kexec is now a submenu titled "Kexec and crash features"
> located under "General Setup".
>
> The following options are impacted:
>
> - KEXEC
> - KEXEC_FILE
> - KEXEC_SIG
> - KEXEC_SIG_FORCE
> - KEXEC_BZIMAGE_VERIFY_SIG
> - KEXEC_JUMP
> - CRASH_DUMP
>
> Over time, these options have been copied between Kconfig files and
> are very similar to one another, but with slight differences.
>
> The following architectures are impacted by the refactor (because of
> use of one or more KEXEC/CRASH options):
>
> - arm
> - arm64
> - ia64
> - loongarch
> - m68k
> - mips
> - parisc
> - powerpc
> - riscv
> - s390
> - sh
> - x86
>
> More information:
>
> In the patch series "crash: Kernel handling of CPU and memory hot
> un/plug"
>
> https://lore.kernel.org/lkml/20230503224145.7405-1-eric.devolder@oracle.com/
>
> the new kernel feature introduces the config option CRASH_HOTPLUG.
>
> In reviewing, Thomas Gleixner requested that the new config option
> not be placed in x86 Kconfig. Rather the option needs a generic/common
> home. To Thomas' point, the KEXEC and CRASH options have largely been
> duplicated in the various arch/<arch>/Kconfig files, with minor
> differences. This kind of proliferation is to be avoid/stopped.
>
> https://lore.kernel.org/lkml/875y91yv63.ffs@tglx/
>
> To that end, I have refactored the arch Kconfigs so as to consolidate
> the various KEXEC and CRASH options. Generally speaking, this work has
> the following themes:
>
> - KEXEC and CRASH options are moved into new file kernel/Kconfig.kexec
> - These items from arch/Kconfig:
> CRASH_CORE KEXEC_CORE KEXEC_ELF HAVE_IMA_KEXEC
> - These items from arch/x86/Kconfig form the common options:
> KEXEC KEXEC_FILE KEXEC_SIG KEXEC_SIG_FORCE
> KEXEC_BZIMAGE_VERIFY_SIG KEXEC_JUMP CRASH_DUMP
> - The crash hotplug series appends CRASH_HOTPLUG to Kconfig.kexec
> NOTE: PHYSICAL_START could be argued to be included in this series.
> - The Kconfig.kexec is now a submenu titled "Kexec and crash features"
> - The Kconfig.kexec is now listed in "General Setup" submenu from
> init/Kconfig
> - To control the main common options, new options ARCH_HAS_KEXEC,
> ARCH_HAS_KEXEC_FILE and ARCH_HAS_CRASH_DUMP are introduced.
> NOTE: I went with ARCH_HAS_ due to the existing ARCH_HAS_KEXEC_PURGATORY.
> - To account for the slight differences, new options ARCH_SUPPORTS_KEXEC,
> ARCH_SUPPORTS_KEXEC_FILE and ARCH_SUPPORTS_CRASH_DUMP are used to
> elicit the same side effects as the original arch/<arch>/Kconfig
> files for KEXEC and CRASH options.
> NOTE: I'm open to a better name than 'ARCH_SUPPORTS', perhaps
> ARCH_CUSTOMIZE ?
>
> An example, 'make menuconfig' illustrating the submenu:
>
> > General setup > Kexec and crash features
> [*] Enable kexec system call
> [*] Enable kexec file based system call
> [*] Verify kernel signature during kexec_file_load() syscall
> [ ] Require a valid signature in kexec_file_load() syscall
> [ ] Enable bzImage signature verification support
> [*] kexec jump
> [*] kernel crash dumps
> [*] Update the crash elfcorehdr on system configuration changes
>
> The three main options are KEXEC, KEXEC_FILE and CRASH_DUMP. In the
> process of consolidating these options, I encountered slight differences
> in the coding of these options in several of the architectures. As a
> result, I settled on the following solution:
>
> - Each of three main options has a 'depends on ARCH_HAS_<option>'
> statement: ARCH_HAS_KEXEC, ARCH_HAS_KEXEC_FILE, ARCH_HAS_CRASH_DUMP.
>
> For example, the KEXEC_FILE option has a 'depends on
> ARCH_HAS_KEXEC_FILE' statement.
>
> - The boolean ARCH_HAS_<option> in effect allows the arch to determine
> when the feature is allowed. Archs which don't have the feature
> simply do not provide the corresponding ARCH_HAS_<option>.
> For each arch, where there previously were KEXEC and/or CRASH
> options, these have been replaced with the corresponding boolean
> ARCH_HAS_<option>, and an appropriate def_bool statement.
>
> For example, if the arch supports KEXEC_FILE, then the
> ARCH_HAS_KEXEC_FILE simply has a 'def_bool y'. This permits the
> KEXEC_FILE option to be available.
>
> If the arch has a 'depends on' statement in its original coding
> of the option, then that expression becomes part of the def_bool
> expression. For example, arm64 had:
>
> config KEXEC
> depends on PM_SLEEP_SMP
>
> and in this solution, this converts to:
>
> config ARCH_HAS_KEXEC
> def_bool PM_SLEEP_SMP
>
>
> - In order to account for the differences in the config coding for
> the three common options, the ARCH_SUPPORTS_<option> is used.
> This options has a 'depends on <option>' statement to couple it
> to the main option, and from there can insert the differences
> from the common option and the arch original coding of that option.
>
> For example, a few archs enable CRYPTO and CRYTPO_SHA256 for
> KEXEC_FILE. These require a ARCH_SUPPORTS_KEXEC_FILE and
> 'select CRYPTO' and 'select CRYPTO_SHA256' statements.
>
> Illustrating the option relationships:
>
> For KEXEC:
> ARCH_HAS_KEXEC <- KEXEC <- ARCH_SUPPORTS_KEXEC
>
> KEXEC # in Kconfig.kexec
> ARCH_HAS_KEXEC # in arch/<arch>/Kconfig, as needed
> ARCH_SUPPORTS_KEXEC # in arch/<arch>/Kconfig, as needed
>
>
> For KEXEC_FILE:
> ARCH_HAS_KEXEC_FILE <- KEXEC_FILE <- ARCH_SUPPORTS_KEXEC_FILE
>
> KEXEC_FILE # in Kconfig.kexec
> ARCH_HAS_KEXEC_FILE # in arch/<arch>/Kconfig, as needed
> ARCH_SUPPORTS_KEXEC_FILE # in arch/<arch>/Kconfig, as needed
>
>
> For CRASH:
> ARCH_HAS_CRASH_DUMP <- CRASH_DUMP <- ARCH_SUPPORTS_CRASH_DUMP
>
> CRASH_DUMP # in Kconfig.kexec
> ARCH_HAS_CRASH_DUMP # in arch/<arch>/Kconfig, as needed
> ARCH_SUPPORTS_CRASH_DUMP # in arch/<arch>/Kconfig, as needed
>
> To summarize, the ARCH_HAS_<option> permits the <option> to be
> enabled, and the ARCH_SUPPORTS_<option> handles side effects (ie.
> select statements).
>
> Examples:
> A few examples to show the new strategy in action:
>
> ===== x86 (minus the help section) =====
> Original:
> config KEXEC
> bool "kexec system call"
> select KEXEC_CORE
>
> config KEXEC_FILE
> bool "kexec file based system call"
> select KEXEC_CORE
> select HAVE_IMA_KEXEC if IMA
> depends on X86_64
> depends on CRYPTO=y
> depends on CRYPTO_SHA256=y
>
> config ARCH_HAS_KEXEC_PURGATORY
> def_bool KEXEC_FILE
>
> config KEXEC_SIG
> bool "Verify kernel signature during kexec_file_load() syscall"
> depends on KEXEC_FILE
>
> config KEXEC_SIG_FORCE
> bool "Require a valid signature in kexec_file_load() syscall"
> depends on KEXEC_SIG
>
> config KEXEC_BZIMAGE_VERIFY_SIG
> bool "Enable bzImage signature verification support"
> depends on KEXEC_SIG
> depends on SIGNED_PE_FILE_VERIFICATION
> select SYSTEM_TRUSTED_KEYRING
>
> config CRASH_DUMP
> bool "kernel crash dumps"
> depends on X86_64 || (X86_32 && HIGHMEM)
>
> config KEXEC_JUMP
> bool "kexec jump"
> depends on KEXEC && HIBERNATION
> help
>
> becomes...
> New:
> config ARCH_HAS_KEXEC
> def_bool y
>
> config ARCH_HAS_KEXEC_FILE
> def_bool X86_64 && CRYPTO && CRYPTO_SHA256
>
> config ARCH_SUPPORTS_KEXEC_FILE
> def_bool y
> depends on KEXEC_FILE
> select HAVE_IMA_KEXEC if IMA
>
> config ARCH_HAS_KEXEC_PURGATORY
> def_bool KEXEC_FILE
>
> config ARCH_HAS_KEXEC_JUMP
> def_bool y
>
> config ARCH_HAS_CRASH_DUMP
> def_bool X86_64 || (X86_32 && HIGHMEM)
>
>
> ===== powerpc (minus the help section) =====
> Original:
> config KEXEC
> bool "kexec system call"
> depends on PPC_BOOK3S || PPC_E500 || (44x && !SMP)
> select KEXEC_CORE
>
> config KEXEC_FILE
> bool "kexec file based system call"
> select KEXEC_CORE
> select HAVE_IMA_KEXEC if IMA
> select KEXEC_ELF
> depends on PPC64
> depends on CRYPTO=y
> depends on CRYPTO_SHA256=y
>
> config ARCH_HAS_KEXEC_PURGATORY
> def_bool KEXEC_FILE
>
> config CRASH_DUMP
> bool "Build a dump capture kernel"
> depends on PPC64 || PPC_BOOK3S_32 || PPC_85xx || (44x && !SMP)
> select RELOCATABLE if PPC64 || 44x || PPC_85xx
>
> becomes...
> New:
> config ARCH_HAS_KEXEC
> def_bool PPC_BOOK3S || PPC_E500 || (44x && !SMP)
>
> config ARCH_HAS_KEXEC_FILE
> def_bool PPC64 && CRYPTO && CRYPTO_SHA256
>
> config ARCH_HAS_KEXEC_PURGATORY
> def_bool KEXEC_FILE
>
> config ARCH_SUPPORTS_KEXEC_FILE
> def_bool y
> depends on KEXEC_FILE
> select KEXEC_ELF
> select HAVE_IMA_KEXEC if IMA
>
> config ARCH_HAS_CRASH_DUMP
> def_bool PPC64 || PPC_BOOK3S_32 || PPC_85xx || (44x && !SMP)
>
> config ARCH_SUPPORTS_CRASH_DUMP
> def_bool y
> depends on CRASH_DUMP
> select RELOCATABLE if PPC64 || 44x || PPC_85xx
>
>
> Testing Approach and Results
>
> There are 388 config files in the arch/<arch>/configs directories.
> For each of these config files, a .config is generated both before and
> after this Kconfig series, and checked for equivalence. This approach
> allows for a rather rapid check of all architectures and a wide
> variety of configs wrt/ KEXEC and CRASH, and avoids requiring
> compiling for all architectures and running kernels and run-time
> testing.
>
> As such, I developed the following script to compare the before and
> after of 'make olddefconfig'. The new symbols introduced by this
> series are filtered out, but otherwise the config files are PASS
> only if they were equivalent, and FAIL otherwise.
>
> The script performs the test by doing the following:
>
> # Obtain the "golden" .config output for given config file
> # Reset test sandbox
> git checkout master
> git branch -D test_Kconfig
> git checkout -B test_Kconfig master
> make distclean
> # Write out updated config
> cp -f <config file> .config
> make ARCH=<arch> olddefconfig
> # Track each item in .config, LHSB is "golden"
> scoreboard .config
>
> # Obtain the "changed" .config output for given config file
> # Reset test sandbox
> make distclean
> # Apply this Kconfig series
> git am <this Kconfig series>
> # Write out updated config
> cp -f <config file> .config
> make ARCH=<arch> olddefconfig
> # Track each item in .config, RHSB is "changed"
> scoreboard .config
>
> # Determine test result
> # Filter-out new symbols introduced by this series
> # Filter-out symbol=n which not in either scoreboard
> # Compare LHSB "golden" and RHSB "changed" scoreboards and issue PASS/FAIL
>
> The script was instrumental during the refactoring of Kconfig as it
> continually revealed problems. The end result being that the solution
> presented in this series passes all configs as checked by the script.
>
> Regards,
> eric
>
>
> ---
> v1: 12jun2023
> - Initial
> - Based on 6.4.0-rc6
>
> ---
> Eric DeVolder (21):
> kexec: consolidate kexec and crash options into kernel/Kconfig.kexec
> x86/kexec: refactor for kernel/Kconfig.kexec
> arm/kexec: refactor for kernel/Kconfig.kexec
> ia64/kexec: refactor for kernel/Kconfig.kexec
> arm64/kexec: refactor for kernel/Kconfig.kexec
> loongarch/kexec: refactor for kernel/Kconfig.kexec
> m68k/kexec: refactor for kernel/Kconfig.kexec
> mips/kexec: refactor for kernel/Kconfig.kexec
> parisc/kexec: refactor for kernel/Kconfig.kexec
> powerpc/kexec: refactor for kernel/Kconfig.kexec
> riscv/kexec: refactor for kernel/Kconfig.kexec
> s390/kexec: refactor for kernel/Kconfig.kexec
> sh/kexec: refactor for kernel/Kconfig.kexec
> crash: move a few code bits to setup support of crash hotplug
> crash: add generic infrastructure for crash hotplug support
> kexec: exclude elfcorehdr from the segment digest
> crash: memory and CPU hotplug sysfs attributes
> x86/crash: add x86 crash hotplug support
> crash: hotplug support for kexec_load()
> crash: change crash_prepare_elf64_headers() to for_each_possible_cpu()
> x86/crash: optimize CPU changes
>
> .../admin-guide/mm/memory-hotplug.rst | 8 +
> Documentation/core-api/cpu_hotplug.rst | 18 +
> arch/Kconfig | 13 -
> arch/arm/Kconfig | 29 +-
> arch/arm64/Kconfig | 61 +--
> arch/ia64/Kconfig | 28 +-
> arch/loongarch/Kconfig | 26 +-
> arch/m68k/Kconfig | 19 +-
> arch/mips/Kconfig | 32 +-
> arch/parisc/Kconfig | 34 +-
> arch/powerpc/Kconfig | 55 +--
> arch/riscv/Kconfig | 48 +--
> arch/s390/Kconfig | 65 +---
> arch/sh/Kconfig | 46 +--
> arch/x86/Kconfig | 90 +----
> arch/x86/include/asm/kexec.h | 18 +
> arch/x86/kernel/crash.c | 140 ++++++-
> drivers/base/cpu.c | 14 +
> drivers/base/memory.c | 13 +
> include/linux/crash_core.h | 9 +
> include/linux/kexec.h | 63 +++-
> include/uapi/linux/kexec.h | 1 +
> init/Kconfig | 2 +
> kernel/Kconfig.kexec | 134 +++++++
> kernel/crash_core.c | 355 ++++++++++++++++++
> kernel/kexec.c | 5 +
> kernel/kexec_core.c | 6 +
> kernel/kexec_file.c | 187 +--------
> kernel/ksysfs.c | 15 +
> 29 files changed, 900 insertions(+), 634 deletions(-)
> create mode 100644 kernel/Kconfig.kexec
>
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