On 05/11/2025 04:40, Ritesh Harjani (IBM) wrote: > Kevin Brodsky <[email protected]> writes: > >> Architectures currently opt in for implementing lazy_mmu helpers by >> defining __HAVE_ARCH_ENTER_LAZY_MMU_MODE. >> >> In preparation for introducing a generic lazy_mmu layer that will >> require storage in task_struct, let's switch to a cleaner approach: >> instead of defining a macro, select a CONFIG option. >> >> This patch introduces CONFIG_ARCH_HAS_LAZY_MMU_MODE and has each >> arch select it when it implements lazy_mmu helpers. >> __HAVE_ARCH_ENTER_LAZY_MMU_MODE is removed and <linux/pgtable.h> >> relies on the new CONFIG instead. >> >> On x86, lazy_mmu helpers are only implemented if PARAVIRT_XXL is >> selected. This creates some complications in arch/x86/boot/, because >> a few files manually undefine PARAVIRT* options. As a result >> <asm/paravirt.h> does not define the lazy_mmu helpers, but this >> breaks the build as <linux/pgtable.h> only defines them if >> !CONFIG_ARCH_HAS_LAZY_MMU_MODE. There does not seem to be a clean >> way out of this - let's just undefine that new CONFIG too. >> >> Signed-off-by: Kevin Brodsky <[email protected]> >> --- >> arch/arm64/Kconfig | 1 + >> arch/arm64/include/asm/pgtable.h | 1 - >> arch/powerpc/include/asm/book3s/64/tlbflush-hash.h | 2 -- >> arch/powerpc/platforms/Kconfig.cputype | 1 + >> arch/sparc/Kconfig | 1 + >> arch/sparc/include/asm/tlbflush_64.h | 2 -- >> arch/x86/Kconfig | 1 + >> arch/x86/boot/compressed/misc.h | 1 + >> arch/x86/boot/startup/sme.c | 1 + >> arch/x86/include/asm/paravirt.h | 1 - >> include/linux/pgtable.h | 2 +- >> mm/Kconfig | 3 +++ >> 12 files changed, 10 insertions(+), 7 deletions(-) > Maybe we can add this to ... ? > > Documentation/features/vm/lazy_mmu/arch-support.txt > > # > # Feature name: lazy_mmu mode > # Kconfig: ARCH_HAS_LAZY_MMU_MODE > # description: arch supports > arch_{enter|flush|leave}_lazy_mmu_mode() > # > ----------------------- > | arch |status| > ----------------------- > | arm64: | ok | > | powerpc: | ok | > | sparc: | ok | > | x86: | ok | > -----------------------
That's an interesting idea but I'm not sure it really makes sense for lazy MMU? AFAIU these arch-support.txt files are meant to help identify which generic features an arch has support for. Lazy MMU isn't really a feature though, in the sense that what it does is entirely defined by the arch. This patch does introduce a generic layer, but ultimately it remains a collection of arch hooks. > As for this patch, the changes are mostly straight forward around the > configs part. This looks good to me. Please feel free to add: > > Reviewed-by: Ritesh Harjani (IBM) <[email protected]> Thanks for the review! - Kevin
