On 2/5/25 15:31, Mark Rutland wrote: > On Wed, Feb 05, 2025 at 10:30:39AM +0530, Anshuman Khandual wrote: >> GENERIC_PTDUMP does not guard any code but instead just used for platform's >> subscription into core ptdump defined under PTDUMP_CORE, which is selected. > > Selected by what? I guess that sentence was incomplete. PTDUMP_CORE gets selected by all the real users which requires core PTDUMP to be built and enabled. arch/arm64/kvm/Kconfig: select PTDUMP_CORE /* config PTDUMP_STAGE2_DEBUGFS */ arch/x86/Kconfig.debug: select PTDUMP_CORE /* config EFI_PGT_DUMP */ mm/Kconfig.debug: select PTDUMP_CORE /* config PTDUMP_DEBUGFS */ mm/Kconfig.debug: select PTDUMP_CORE /* config DEBUG_WX */ > >> Instead use PTDUMP_CORE for platform subscription and drop GENERIC_PTDUMP. >> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> >> Cc: Will Deacon <will@xxxxxxxxxx> >> Cc: Jonathan Corbet <corbet@xxxxxxx> >> Cc: Marc Zyngier <maz@xxxxxxxxxx> >> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> >> Cc: Nicholas Piggin <npiggin@xxxxxxxxx> >> Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx> >> Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx> >> Cc: Heiko Carstens <hca@xxxxxxxxxxxxx> >> Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx> >> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> >> Cc: Ingo Molnar <mingo@xxxxxxxxxx> >> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> >> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx >> Cc: linux-doc@xxxxxxxxxxxxxxx >> Cc: linux-kernel@xxxxxxxxxxxxxxx >> Cc: kvmarm@xxxxxxxxxxxxxxx >> Cc: linuxppc-dev@xxxxxxxxxxxxxxxx >> Cc: linux-riscv@xxxxxxxxxxxxxxxxxxx >> Cc: linux-s390@xxxxxxxxxxxxxxx >> Cc: linux-mm@xxxxxxxxx >> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx> >> --- >> This patch applies on v6.14-rc1 >> >> Changes in V2: >> >> - Keep arch/powerpc/Kconfig alphabetically sorted per Christophe >> >> Changes in V1: >> >> https://lore.kernel.org/all/20241217034807.2541349-1-anshuman.khandual@xxxxxxx/ >> >> Documentation/arch/arm64/ptdump.rst | 1 - >> arch/arm64/Kconfig | 2 +- >> arch/arm64/kvm/Kconfig | 3 +-- >> arch/powerpc/Kconfig | 2 +- >> arch/powerpc/configs/mpc885_ads_defconfig | 1 - >> arch/riscv/Kconfig | 2 +- >> arch/s390/Kconfig | 2 +- >> arch/x86/Kconfig | 2 +- >> arch/x86/Kconfig.debug | 2 +- >> kernel/configs/debug.config | 1 - >> mm/Kconfig.debug | 8 ++------ >> 11 files changed, 9 insertions(+), 17 deletions(-) >> >> diff --git a/Documentation/arch/arm64/ptdump.rst b/Documentation/arch/arm64/ptdump.rst >> index 5dcfc5d7cddf..61ca040a885b 100644 >> --- a/Documentation/arch/arm64/ptdump.rst >> +++ b/Documentation/arch/arm64/ptdump.rst >> @@ -22,7 +22,6 @@ offlining of memory being accessed by the ptdump code. >> In order to dump the kernel page tables, enable the following >> configurations and mount debugfs:: >> >> - CONFIG_GENERIC_PTDUMP=y >> CONFIG_PTDUMP_CORE=y >> CONFIG_PTDUMP_DEBUGFS=y >> >> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >> index fcdd0ed3eca8..1f516bed81dd 100644 >> --- a/arch/arm64/Kconfig >> +++ b/arch/arm64/Kconfig >> @@ -157,7 +157,7 @@ config ARM64 >> select GENERIC_IRQ_SHOW_LEVEL >> select GENERIC_LIB_DEVMEM_IS_ALLOWED >> select GENERIC_PCI_IOMAP >> - select GENERIC_PTDUMP >> + select PTDUMP_CORE >> select GENERIC_SCHED_CLOCK >> select GENERIC_SMP_IDLE_THREAD >> select GENERIC_TIME_VSYSCALL > > This change means that the ptdump core code will be built regardless of > whether any users are selected: > > [mark@lakrids:~/src/linux]% git grep CONFIG_PTDUMP_CORE > Documentation/arch/arm64/ptdump.rst: CONFIG_PTDUMP_CORE=y > arch/arm64/include/asm/ptdump.h:#ifdef CONFIG_PTDUMP_CORE > arch/arm64/include/asm/ptdump.h:#endif /* CONFIG_PTDUMP_CORE */ > arch/arm64/mm/Makefile:obj-$(CONFIG_PTDUMP_CORE) += ptdump.o > arch/powerpc/mm/Makefile:obj-$(CONFIG_PTDUMP_CORE) += ptdump/ > arch/riscv/mm/Makefile:obj-$(CONFIG_PTDUMP_CORE) += ptdump.o > arch/s390/mm/Makefile:obj-$(CONFIG_PTDUMP_CORE) += dump_pagetables.o > arch/x86/mm/Makefile:obj-$(CONFIG_PTDUMP_CORE) += dump_pagetables.o > mm/Makefile:obj-$(CONFIG_PTDUMP_CORE) += ptdump.o > > GENERIC_PTDUMP means "this architecture uses generic ptdump code for > ptdump", i.e. the architecture implements all the necessary bits for > that to work *IF* it is built. > > PTDUMP_CORE means "actually build the core ptdump code". > > If everyone uses the generic ptdump code now, maybe it's worth renaming > GENERIC_PTDUMP to ARCH_HAS_PTDUMP or something like that, but I don't > think this change makes sense as-is. Seems like a combination of ARCH_HAS_CORE_PTDUMP for subscription and CORE_PTDUMP for actual enablement will make things clear. _CORE_ here would still let platforms define their own CONFIG_PTDUMP if preferred and not subscribe the generic CORE_DUMP. currently GENERIC_PTDUMP and CORE_PTDUMP just seems disjoint, because GENERIC_PTDUMP does not not appear to be the platform opt in required for CORE_PTDUMP. There is another problem. mm/Kconfig.debug config DEBUG_WX bool "Warn on W+X mappings at boot" depends on ARCH_HAS_DEBUG_WX depends on MMU select PTDUMP_CORE help Before selecting PTDUMP_CORE it does not ensure platform has opted in via GENERIC_PTDUMP or not. Instead it should be config DEBUG_WX bool "Warn on W+X mappings at boot" depends on ARCH_HAS_DEBUG_WX depends on GENERIC_PTDUMP depends on depends on MMU select PTDUMP_CORE help PTDUMP_STAGE2_DEBUGFS on arm64 does that where as EFI_PGT_DUMP on x86 does not. Although it will be ideal but that's not a problem if the platform knows for sure that it opts in GENERIC_PTDUMP. > > [...] > >> diff --git a/kernel/configs/debug.config b/kernel/configs/debug.config >> index 20552f163930..8aafd050b754 100644 >> --- a/kernel/configs/debug.config >> +++ b/kernel/configs/debug.config >> @@ -73,7 +73,6 @@ CONFIG_DEBUG_VM=y >> CONFIG_DEBUG_VM_PGFLAGS=y >> CONFIG_DEBUG_VM_RB=y >> CONFIG_DEBUG_VM_VMACACHE=y >> -CONFIG_GENERIC_PTDUMP=y >> CONFIG_KASAN=y >> CONFIG_KASAN_GENERIC=y >> CONFIG_KASAN_INLINE=y > > I think this is wrong today, and removing it is the right thing to do. > > Architectures with support will select this themselves, and on > architectures without support this either does nothing or causes a build > failure. Alright, will separate this change out first.
