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Date:   Fri, 27 Aug 2021 19:10:41 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Christoph Hellwig <hch@lst.de>, Will Deacon <will@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Android Kernel Team <kernel-team@android.com>
Subject: Re: [GIT PULL] arm64 fix for 5.14
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On Fri, Aug 27, 2021 at 10:03:29AM -0700, Linus Torvalds wrote:
> The ARM code actually uses that complex pfn_to_section_nr() and
> memblock_is_memory() etc. That seems a bit of an overkill, since the
> memblock code should have translated all that into being reserved.
> 
> But again, I don't actually know exactly what triggered the issue on
> ARM, so the above is just my "this seems to be a more proper check"
> suggestion.

They CCed me on their earlier discussion, but I did not catch up on it
until you responded to the pull request  If I understood it correct it
was about a platform device mapping a MMIO region (like a PCI bar),
but something about section alignment cause pfn_valid to mistrigger.