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Date:   Tue, 30 Apr 2019 04:32:53 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Robin Murphy <robin.murphy@arm.com>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Tom Murphy <tmurphy@arista.com>,
        iommu@lists.linux-foundation.org, Heiko Stuebner <heiko@sntech.de>,
        Will Deacon <will.deacon@arm.com>,
        David Brown <david.brown@linaro.org>,
        Thierry Reding <thierry.reding@gmail.com>,
        linux-s390@vger.kernel.org, linux-samsung-soc@vger.kernel.org,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        linux-rockchip@lists.infradead.org, Kukjin Kim <kgene@kernel.org>,
        Gerald Schaefer <gerald.schaefer@de.ibm.com>,
        Andy Gross <andy.gross@linaro.org>,
        linux-tegra@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        linux-mediatek@lists.infradead.org,
        Matthias Brugger <matthias.bgg@gmail.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        murphyt7@tcd.ie, David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH v2 3/4] iommu/dma-iommu: Use the dev->coherent_dma_mask
Message-ID: <20190430113253.GA23210@infradead.org>
References: <20190430002952.18909-1-tmurphy@arista.com>
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 <20190430111222.GA3191@infradead.org>
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On Tue, Apr 30, 2019 at 12:27:02PM +0100, Robin Murphy wrote:
> > Hmm, I don't think we need the DMA mask for the MSI mapping, this
> > should probably always use a 64-bit mask.
> 
> If that were true then we wouldn't need DMA masks for regular mappings
> either. If we have to map the MSI doorbell at all, then we certainly have to
> place it at an IOVA that the relevant device is actually capable of
> addressing.

Well, as shown by the patch below we don't even look at the DMA mask
for the MSI page - we just allocate from bottom to top.