From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 55D0CC02198 for ; Thu, 6 Feb 2025 04:23:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=AuAgdwDajVK2vGTyHl3+wr9kL1qPUEk2o7H/YzCfeIA=; b=b5kgAa848bUWrO5UnE3+mT+qBW AAllGQ9j70kkfDnb328sdYbI0MKbuCuU4Y3P7toWZT34VIhc5kddPupJN7FwQ/sdrJdUWwRra+3aT Oz1TcOlunDzHIw2pZx0if4rMuHR9AmT00Z/4up7vASG4/Kye+jeP+nwTQJ3FXYqMU4SILilHMXyQX 8hdgMDcPo7WDgZD5ElZ1rCUpEmU9Fb4w2P6qxcsSJFz/q+khiUCdmMAF2lFaAHNfKLlfyVqmRsZJ3 cQt6wZU9TQhevQuyEkxjij2G0X/wiZGrX1CIcZnCz6AFAYwIwC3h3VxfW4iru5Fup2enIe7xyNkff 9wymJ5vg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tftQD-00000005B9Y-27p6; Thu, 06 Feb 2025 04:23:25 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tftOn-00000005B2x-3y1Q; Thu, 06 Feb 2025 04:21:59 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 823831007; Wed, 5 Feb 2025 20:22:19 -0800 (PST) Received: from [10.163.34.115] (unknown [10.163.34.115]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id F38B13F5A1; Wed, 5 Feb 2025 20:21:48 -0800 (PST) Message-ID: Date: Thu, 6 Feb 2025 09:51:45 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V2] mm/ptdump: Drop GENERIC_PTDUMP To: Mark Rutland Cc: linux-mm@kvack.org, steven.price@arm.com, christophe.leroy@csgroup.eu, Catalin Marinas , Will Deacon , Jonathan Corbet , Marc Zyngier , Michael Ellerman , Nicholas Piggin , Paul Walmsley , Palmer Dabbelt , Heiko Carstens , Vasily Gorbik , Thomas Gleixner , Ingo Molnar , Andrew Morton , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org References: <20250205050039.1506377-1-anshuman.khandual@arm.com> Content-Language: en-US From: Anshuman Khandual In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250205_202158_080556_898E973F X-CRM114-Status: GOOD ( 26.79 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 >> Cc: Will Deacon >> Cc: Jonathan Corbet >> Cc: Marc Zyngier >> Cc: Michael Ellerman >> Cc: Nicholas Piggin >> Cc: Paul Walmsley >> Cc: Palmer Dabbelt >> Cc: Heiko Carstens >> Cc: Vasily Gorbik >> Cc: Thomas Gleixner >> Cc: Ingo Molnar >> Cc: Andrew Morton >> Cc: linux-arm-kernel@lists.infradead.org >> Cc: linux-doc@vger.kernel.org >> Cc: linux-kernel@vger.kernel.org >> Cc: kvmarm@lists.linux.dev >> Cc: linuxppc-dev@lists.ozlabs.org >> Cc: linux-riscv@lists.infradead.org >> Cc: linux-s390@vger.kernel.org >> Cc: linux-mm@kvack.org >> Signed-off-by: Anshuman Khandual >> --- >> 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@arm.com/ >> >> 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.