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Message-ID: <20190415063058.GA1377@infradead.org> Date: Sun, 14 Apr 2019 23:30:58 -0700 From: Christoph Hellwig <hch@...radead.org> To: Tom Murphy <tmurphy@...sta.com> Cc: iommu@...ts.linux-foundation.org, Heiko Stuebner <heiko@...ech.de>, Will Deacon <will.deacon@....com>, David Brown <david.brown@...aro.org>, linux-samsung-soc@...r.kernel.org, dima@...sta.com, Krzysztof Kozlowski <krzk@...nel.org>, linux-rockchip@...ts.infradead.org, Kukjin Kim <kgene@...nel.org>, Andy Gross <andy.gross@...aro.org>, Marc Zyngier <marc.zyngier@....com>, linux-arm-msm@...r.kernel.org, linux-mediatek@...ts.infradead.org, Matthias Brugger <matthias.bgg@...il.com>, Thomas Gleixner <tglx@...utronix.de>, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, murphyt7@....ie, Robin Murphy <robin.murphy@....com> Subject: Re: [PATCH 1/9] iommu/dma-iommu: Add iommu_map_atomic On Thu, Apr 11, 2019 at 07:47:30PM +0100, Tom Murphy via iommu wrote: > The iommu ops .map function (or the iommu_map function which calls it) > was always supposed to be sleepable (according to Joerg's comment in > this thread: https://lore.kernel.org/patchwork/patch/977520/ ) and so > should probably have had a "might_sleep()" since it was written. However > currently the dma-iommu api can call iommu_map in an atomic context, > which it shouldn't do. This doesn't cause any problems because any iommu > driver which uses the dma-iommu api uses gfp_atomic in it's iommu_ops > .map function. But doing this wastes the memory allocators atomic pools. > > Add a new function iommu_map_atomic, use it in the dma-iommu api and add > “might_sleep()” to the iommu_map function. > > After this change all drivers which use the dma-iommu api need to > implement the new iommu ops .map_atomic function. For the moment just > reuse the driver's iommus ops .map function for .map_atomic. Instead of duplicating the callchain shouldn't we just pass down a flag to indicate if the context can sleep or not? Especially as all the existing arm drivers already implement the atomic behavior, which is a majority of struct iommu_ops based iommu drivers.
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