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Date:   Tue, 21 Sep 2021 17:38:05 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Mike Rapoport <rppt@kernel.org>
Cc:     Christoph Hellwig <hch@lst.de>,
        Catalin Marinas <catalin.marinas@arm.com>,
        David Hildenbrand <david@redhat.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Alex Bee <knaerzche@gmail.com>, Will Deacon <will@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Anshuman Khandual <anshuman.khandual@arm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-mm@kvack.org,
        Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [BUG 5.14] arm64/mm: dma memory mapping fails (in some cases)
Message-ID: <20210921153805.GA29952@lst.de>
References: <0908ce39-7e30-91fa-68ef-11620f9596ae@arm.com> <60a11eba-2910-3b5f-ef96-97d4556c1596@redhat.com> <20210825102044.GA3420@arm.com> <YUUHJ5EI+6Mop4Wu@kernel.org> <20210918051843.GA16104@lst.de> <YUWlO2tZC5IwCAHV@kernel.org> <YUXQBV6KKi+/Q6gX@kernel.org> <YUhpNgwwttW1ewez@arm.com> <20210921082007.GA29121@lst.de> <YUmnEoifUsnvAiuV@kernel.org>
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On Tue, Sep 21, 2021 at 12:34:10PM +0300, Mike Rapoport wrote:
> > It doesn't create any new mappings.  The only real issue is that it
> > does the wrong thing for RAM in a way that might not be noticed on
> > simple (x86/PC) platforms.
> 
> But if the mapping request was rejected by devm_ioremap_resource() because
> of an attempt to map RAM, why we would get to dma_map_resource() at all? 

dma_map_resource takes a phys_addr_t that could come from anywhere.