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Date:   Wed, 15 Sep 2021 09:45:57 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     guoren@kernel.org
Cc:     anup.patel@wdc.com, atish.patra@wdc.com, palmerdabbelt@google.com,
        christoph.muellner@vrull.eu, philipp.tomsich@vrull.eu, hch@lst.de,
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        linux-kernel@vger.kernel.org, taiten.peng@canonical.com,
        aniket.ponkshe@canonical.com, heinrich.schuchardt@canonical.com,
        gordan.markus@canonical.com, Guo Ren <guoren@linux.alibaba.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Palmer Dabbelt <palmer@dabbelt.com>
Subject: Re: [RFC PATCH V4 1/6] riscv: pgtable: Add custom protection_map
 init
Message-ID: <20210915074557.GA20024@lst.de>
References: <20210911092139.79607-1-guoren@kernel.org> <20210911092139.79607-2-guoren@kernel.org>
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On Sat, Sep 11, 2021 at 05:21:34PM +0800, guoren@kernel.org wrote:
> From: Guo Ren <guoren@linux.alibaba.com>
> 
> Some RISC-V CPU vendors have defined their own PTE attributes to
> solve non-coherent DMA bus problems. That makes _P/SXXX definitions
> contain global variables which could be initialized at the early
> boot stage before setup_vm. The patch prevents compile errors.

That sounds way to nice for someone who deliberatly ignores the
specification and should definitively not go into the kernel
commit log like this.

> This patch is similar to 316d097c4cd4  (x86/pti: Filter at
> vma->vm_page_prot population) which give a choice for arch custom
> implementation.

How?  To me it looks like a bad duplication of such functionality in
a way that totally breaks abstractions.  architectures really do not
have any business changing protection_map.