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Date: Mon, 9 Jan 2017 12:59:59 -0800
From: Christoph Hellwig <hch@infradead.org>
To: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Cc: Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Artemi Ivanov <artemi.ivanov@cogentembedded.com>
Subject: Re: blk_queue_bounce_limit() broken for mask=0xffffffff on 64bit
 archs
Message-ID: <20170109205959.GA1112@infradead.org>
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On Mon, Jan 09, 2017 at 11:48:11PM +0300, Nikita Yushchenko wrote:
> Hi
> 
> There is a use cases when architecture is 64-bit but hardware supports
> only DMA to lower 4G of address space. E.g. NVMe device on RCar PCIe host.

The solution is to shoot the SOC designer.  If that doesn't work use
swiotlb.