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Message-ID: <27980882-4433-443f-abd1-ea5d96b687ea@arm.com> Date: Wed, 18 Dec 2024 12:29:40 +0530 From: Anshuman Khandual <anshuman.khandual@....com> To: Christophe Leroy <christophe.leroy@...roup.eu>, linux-mm@...ck.org Cc: steven.price@....com, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Jonathan Corbet <corbet@....net>, Marc Zyngier <maz@...nel.org>, Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>, Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, kvmarm@...ts.linux.dev, linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org Subject: Re: [PATCH] mm/ptdump: Drop GENERIC_PTDUMP On 12/17/24 13:17, Christophe Leroy wrote: > > > Le 17/12/2024 à 04:48, Anshuman Khandual a écrit : >> 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. >> Instead use PTDUMP_CORE for platform subscription and drop GENERIC_PTDUMP. >> >> Cc: Catalin Marinas <catalin.marinas@....com> >> Cc: Will Deacon <will@...nel.org> >> Cc: Jonathan Corbet <corbet@....net> >> Cc: Marc Zyngier <maz@...nel.org> >> Cc: Michael Ellerman <mpe@...erman.id.au> >> Cc: Nicholas Piggin <npiggin@...il.com> >> Cc: Paul Walmsley <paul.walmsley@...ive.com> >> Cc: Palmer Dabbelt <palmer@...belt.com> >> Cc: Heiko Carstens <hca@...ux.ibm.com> >> Cc: Vasily Gorbik <gor@...ux.ibm.com> >> Cc: Thomas Gleixner <tglx@...utronix.de> >> Cc: Ingo Molnar <mingo@...hat.com> >> Cc: Andrew Morton <akpm@...ux-foundation.org> >> Cc: linux-arm-kernel@...ts.infradead.org >> Cc: linux-doc@...r.kernel.org >> Cc: linux-kernel@...r.kernel.org >> Cc: kvmarm@...ts.linux.dev >> Cc: linuxppc-dev@...ts.ozlabs.org >> Cc: linux-riscv@...ts.infradead.org >> Cc: linux-s390@...r.kernel.org >> Cc: linux-mm@...ck.org >> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com> >> --- >> This patch applies on v6.13-rc3 and has been tested on arm64, although it >> also clears build tests on impacted platforms. >> >> 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/arch/powerpc/Kconfig b/arch/powerpc/Kconfig >> index a0ce777f9706..c716f8df10de 100644 >> --- a/arch/powerpc/Kconfig >> +++ b/arch/powerpc/Kconfig >> @@ -203,7 +203,7 @@ config PPC >> select GENERIC_IRQ_SHOW >> select GENERIC_IRQ_SHOW_LEVEL >> select GENERIC_PCI_IOMAP if PCI >> - select GENERIC_PTDUMP >> + select PTDUMP_CORE > > Please keep alphabetical order. Sure, will do that. > >> select GENERIC_SMP_IDLE_THREAD >> select GENERIC_TIME_VSYSCALL >> select GENERIC_VDSO_TIME_NS > >> diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug >> index 41a58536531d..b206e5a11f96 100644 >> --- a/mm/Kconfig.debug >> +++ b/mm/Kconfig.debug >> @@ -187,7 +187,7 @@ config DEBUG_WX >> bool "Warn on W+X mappings at boot" >> depends on ARCH_HAS_DEBUG_WX >> depends on MMU >> - select PTDUMP_CORE >> + depends on PTDUMP_CORE > > This change is unclear to me. It works because all arch selecting ARCH_HAS_DEBUG_WX also select GENERIC_PTDUMP. For riscv it's even more tricking, Riscv only selects GENERIC_PTDUMP when MMU is set, so it works because here it also depends on MMU. Right, all the archs selecting ARCH_HAS_DEBUG_WX also select PTDUMP_CORE. DEBUG_WX dependency on PTDUMP_CORE will always be met, when the platform selects ARCH_HAS_DEBUG_WX as expected. git grep "select PTDUMP_CORE" arch/ arch/arm64/Kconfig: select PTDUMP_CORE arch/powerpc/Kconfig: select PTDUMP_CORE arch/riscv/Kconfig: select PTDUMP_CORE if MMU arch/s390/Kconfig: select PTDUMP_CORE arch/x86/Kconfig: select PTDUMP_CORE git grep ARCH_HAS_DEBUG_WX arch/ arch/arm64/Kconfig: select ARCH_HAS_DEBUG_WX arch/powerpc/Kconfig: select ARCH_HAS_DEBUG_WX if STRICT_KERNEL_RWX arch/riscv/Kconfig: select ARCH_HAS_DEBUG_WX arch/s390/Kconfig: select ARCH_HAS_DEBUG_WX arch/x86/Kconfig: select ARCH_HAS_DEBUG_WX On riscv platform, does not PTDUMP_CORE implicitly imply existence of MMU ? Could there be a page table dumper without a MMU. > > But what happens if in the future an architecture selects ARCH_HAS_DEBUG_WX without selecting PTDUMP_CORE ? Should DEBUG_WX just select PTDUMP_CORE as it exists now. A platform will be able to get PTDUMP_CORE via DEBUG_WX if ARCH_HAS_DEBUG_WX is subscribed into. Would that be better ? > > >> help >> Generate a warning if any W+X mappings are found at boot. >> @@ -212,9 +212,6 @@ config DEBUG_WX >> If in doubt, say "Y". >> -config GENERIC_PTDUMP >> - bool >> - >> config PTDUMP_CORE >> bool >> @@ -222,8 +219,7 @@ config PTDUMP_DEBUGFS >> bool "Export kernel pagetable layout to userspace via debugfs" >> depends on DEBUG_KERNEL >> depends on DEBUG_FS >> - depends on GENERIC_PTDUMP >> - select PTDUMP_CORE >> + depends on PTDUMP_CORE >> help >> Say Y here if you want to show the kernel pagetable layout in a >> debugfs file. This information is only useful for kernel developers >
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