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Linux aarch64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH] Fix folio conversion in __dma_page_dev_to_cpu() Content-Language: en-GB To: Matthew Wilcox Cc: Russell King , Andrew Morton , Marek Szyprowski , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org References: <20230823191852.1556561-1-willy@infradead.org> <46702101-01b3-1d1d-e5c0-f869c5b88ea5@arm.com> From: Robin Murphy In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: C0562140007 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: tq5o3fhrtr1u8g3k8ge7iz7defk9osz8 X-HE-Tag: 1692897297-783708 X-HE-Meta: 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 2br5Rl6S QKfhsKey9WN/eHE9XD8xPBQen47l9L/9SCVQmVdzrQlmws6FjHr7kx96qQdzCGkXAMaiph6fMz3sXKwUH7wEwydc37a4O5Vw3fSMfHGtXUQjQB9Tsw18kXAgeU69BiFCgAsBOMv7OOZttm0w/TyaeGzuOiA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 24/08/2023 5:49 pm, Matthew Wilcox wrote: > On Thu, Aug 24, 2023 at 05:39:38PM +0100, Robin Murphy wrote: >> As for >2GB segments, we've certainly seen cases of users mapping absurdly >> large buffers and overflowing dma_length[2], so I would imagine it's only >> the improbability of allocating that much physically-contiguous memory which >> keeps individual segment lengths from getting up to UINT_MAX ;) > > With a 32-bit kernel though? ;-) Oh, indeed, that's more of a challenge... I guess take an LPAE system with enough RAM, run VMSPLIT_3G and convince a dma-buf heap to let you import ~2.5GB of contiguous highmem for some kind of in-place media processing, maybe? Not exactly 4, but still more than 2. In principle :D Robin.