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Date:   Tue, 6 Aug 2019 17:46:02 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     "Lendacky, Thomas" <Thomas.Lendacky@amd.com>
Cc:     Lucas Stach <l.stach@pengutronix.de>,
        Christoph Hellwig <hch@lst.de>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Thiago Jung Bauermann <bauerman@linux.ibm.com>,
        Halil Pasic <pasic@linux.ibm.com>
Subject: Re: Regression due to d98849aff879 (dma-direct: handle
 DMA_ATTR_NO_KERNEL_MAPPING in common code)
Message-ID: <20190806154602.GB25050@lst.de>
References: <1565082809.2323.24.camel@pengutronix.de> <20190806113318.GA20215@lst.de> <41cc93b1-62b5-7fb6-060d-01982e68503b@amd.com> <20190806140408.GA22902@lst.de> <1565100418.2323.32.camel@pengutronix.de> <78833204-cd30-1a4b-54e3-1580018c6d57@amd.com>
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On Tue, Aug 06, 2019 at 02:18:49PM +0000, Lendacky, Thomas wrote:
> I think you need to keep everything inside the original if statement since
> the caller is expecting a page pointer to be returned in this case and not
> the page_address() which is returned when the DMA_ATTR_NO_KERNEL_MAPPING
> is not present.

DMA_ATTR_NO_KERNEL_MAPPING is defined to return an opaque cookie,
which just happens to be a page pointer.  So if we fix up the free side
as pointed out by Lucas we should be fine.