linux-kernel - Re: [PATCH 0/3] arm64/ptdump: Add cmdline 'early

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Message-ID: <aMv00p44PyZZv7cH@willie-the-truck>
Date: Thu, 18 Sep 2025 13:02:26 +0100
From: Will Deacon <will@...nel.org>
To: Anshuman Khandual <anshuman.khandual@....com>
Cc: linux-arm-kernel@...ts.infradead.org,
	Catalin Marinas <catalin.marinas@....com>,
	Mark Brown <broonie@...nel.org>,
	Ryan Roberts <ryan.roberts@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Ritesh Harjani <ritesh.list@...il.com>,
	linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org
Subject: Re: [PATCH 0/3] arm64/ptdump: Add cmdline 'early_ptdump'

On Wed, Sep 10, 2025 at 03:16:20PM +0530, Anshuman Khandual wrote:
> Enable early kernel page table dump for debug purpose when required through
> a new kernel command line option 'early_ptdump'. But first this reorganizes
> ptdump_init() separating out the debugfs creation, so that it can be called
> early on in setup_arch(). This also adds kernel dmesg console print support
> for existing pt_dump_seq_[printf|puts]() helpers.
> 
> This series applies on v6.17-rc5
> 
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Mark Brown <broonie@...nel.org>
> Cc: Ryan Roberts <ryan.roberts@....com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Ard Biesheuvel <ardb@...nel.org>
> Cc: Ritesh Harjani (IBM) <ritesh.list@...il.com>
> Cc: linux-kernel@...r.kernel.org
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-efi@...r.kernel.org

I'm really not convinced this is particularly useful and I've certainly
never felt the need to have something like it. If you're debugging really
early page-table issues, why you want to rely on all the ptdump
infrastructure to get logs out?

On the other hand, if people do find this useful, then I think it should
be implemented in the core code rather than done behind its back in the
arch code.

Will