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Date:   Thu, 4 Nov 2021 18:20:37 +0000
From:   "Russell King (Oracle)" <linux@armlinux.org.uk>
To:     Catalin Marinas <catalin.marinas@arm.com>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Matthew Wilcox <willy@infradead.org>,
        Christoph Hellwig <hch@lst.de>,
        linux-arch <linux-arch@vger.kernel.org>,
        Ira Weiny <ira.weiny@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: flush_dcache_page vs kunmap_local
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On Thu, Nov 04, 2021 at 06:04:45PM +0000, Catalin Marinas wrote:
> The cachetlb.rst doc states the two cases where flush_dcache_page()
> should be called:
> 
> 1. After writing to a page cache page (that's what we need on arm64 for
>    the I-cache).
> 
> 2. Before reading from a page cache page and user mappings potentially
>    exist. I think arm32 ensures the D-cache user aliases are coherent
>    with the kernel one (added rmk to confirm).

Yes, where necessary, we flush the user aliases in flush_dcache_page().

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