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Date:   Thu, 17 Aug 2023 11:12:45 +0100
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     Arnd Bergmann <arnd@kernel.org>
Cc:     Will Deacon <will@kernel.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Tiezhu Yang <yangtiezhu@loongson.cn>,
        loongarch@lists.linux.dev, WANG Xuerui <kernel@xen0n.name>,
        Huacai Chen <chenhuacai@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Nathan Chancellor <nathan@kernel.org>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-riscv@lists.infradead.org
Subject: Re: [PATCH] asm-generic: partially revert "Unify uapi bitsperlong.h
 for arm64, riscv and loongarch"
Message-ID: <ZN3ynbHyY4SE05ZQ@arm.com>
References: <20230811204930.1529925-1-arnd@kernel.org>
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On Fri, Aug 11, 2023 at 10:49:07PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> Unifying the asm-generic headers across 32-bit and 64-bit architectures
> based on the compiler provided macros was a good idea and appears to work
> with all user space, but it caused a regression when building old kernels
> on systems that have the new headers installed in /usr/include, as this
> combination trips an inconsistency in the kernel's own tools/include
> headers that are a mix of userspace and kernel-internal headers.
> 
> This affects kernel builds on arm64, riscv64 and loongarch64 systems that
> might end up using the "#define __BITS_PER_LONG 32" default from the old
> tools headers. Backporting the commit into stable kernels would address
> this, but it would still break building kernels without that backport,
> and waste time for developers trying to understand the problem.
> 
> arm64 build machines are rather common, and on riscv64 this can also
> happen in practice, but loongarch64 is probably new enough to not
> be used much for building old kernels, so only revert the bits
> for arm64 and riscv.
> 
> Link: https://lore.kernel.org/all/20230731160402.GB1823389@dev-arch.thelio-3990X/
> Reported-by: Nathan Chancellor <nathan@kernel.org>
> Fixes: 8386f58f8deda ("asm-generic: Unify uapi bitsperlong.h for arm64, riscv and loongarch")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

For arm64:

Acked-by: Catalin Marinas <catalin.marinas@arm.com>