From: Robin Murphy <robin.murphy@arm.com> To: David Stevens <stevensd@chromium.org>, Will Deacon <will@kernel.org> Cc: Joerg Roedel <joro@8bytes.org>, Lu Baolu <baolu.lu@linux.intel.com>, Tom Murphy <murphyt7@tcd.ie>, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 3/5] dma-iommu: add SKIP_CPU_SYNC after syncing Date: Wed, 11 Aug 2021 20:00:35 +0100 [thread overview] Message-ID: <d8f07858-e8e7-9989-b95f-c512ba3904cf@arm.com> (raw) In-Reply-To: <20210811024247.1144246-4-stevensd@google.com> On 2021-08-11 03:42, David Stevens wrote: > From: David Stevens <stevensd@chromium.org> > > After syncing in map/unmap, add the DMA_ATTR_SKIP_CPU_SYNC flag so > anything that uses attrs later on will skip any sync work that has > already been completed. In particular, this skips copying from the > swiotlb twice during unmap. > > Signed-off-by: David Stevens <stevensd@chromium.org> > --- > drivers/iommu/dma-iommu.c | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index 4f0cc4a0a61f..be0214b1455c 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -859,8 +859,11 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page, > static void iommu_dma_unmap_page(struct device *dev, dma_addr_t dma_handle, > size_t size, enum dma_data_direction dir, unsigned long attrs) > { > - if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) > + if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) { > iommu_dma_sync_single_for_cpu(dev, dma_handle, size, dir); > + attrs |= DMA_ATTR_SKIP_CPU_SYNC; > + } > + > __iommu_dma_unmap_swiotlb(dev, dma_handle, size, dir, attrs); Again, fold that into here and put the arch sync in an else case to the is_swiotlb_buffer() check. > } > > @@ -999,8 +1002,10 @@ static int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg, > if (dev_is_untrusted(dev)) > return iommu_dma_map_sg_swiotlb(dev, sg, nents, dir, attrs); > > - if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) > + if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) { > iommu_dma_sync_sg_for_device(dev, sg, nents, dir); > + attrs |= DMA_ATTR_SKIP_CPU_SYNC; > + } Why? attrs is never referenced again after this. > /* > * Work out how much IOVA space we need, and align the segments to > @@ -1068,8 +1073,10 @@ static void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, > struct scatterlist *tmp; > int i; > > - if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) > + if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) { > iommu_dma_sync_sg_for_cpu(dev, sg, nents, dir); > + attrs |= DMA_ATTR_SKIP_CPU_SYNC; > + } Just move it down so it's out of the SWIOTLB path entirely. Exactly like you did in patch #2 for map_sg, conspicuous in the hunk above. Robin. > > if (dev_is_untrusted(dev)) { > iommu_dma_unmap_sg_swiotlb(dev, sg, nents, dir, attrs); >
WARNING: multiple messages have this Message-ID (diff)
From: Robin Murphy <robin.murphy@arm.com> To: David Stevens <stevensd@chromium.org>, Will Deacon <will@kernel.org> Cc: linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, Tom Murphy <murphyt7@tcd.ie> Subject: Re: [PATCH v3 3/5] dma-iommu: add SKIP_CPU_SYNC after syncing Date: Wed, 11 Aug 2021 20:00:35 +0100 [thread overview] Message-ID: <d8f07858-e8e7-9989-b95f-c512ba3904cf@arm.com> (raw) In-Reply-To: <20210811024247.1144246-4-stevensd@google.com> On 2021-08-11 03:42, David Stevens wrote: > From: David Stevens <stevensd@chromium.org> > > After syncing in map/unmap, add the DMA_ATTR_SKIP_CPU_SYNC flag so > anything that uses attrs later on will skip any sync work that has > already been completed. In particular, this skips copying from the > swiotlb twice during unmap. > > Signed-off-by: David Stevens <stevensd@chromium.org> > --- > drivers/iommu/dma-iommu.c | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index 4f0cc4a0a61f..be0214b1455c 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -859,8 +859,11 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page, > static void iommu_dma_unmap_page(struct device *dev, dma_addr_t dma_handle, > size_t size, enum dma_data_direction dir, unsigned long attrs) > { > - if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) > + if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) { > iommu_dma_sync_single_for_cpu(dev, dma_handle, size, dir); > + attrs |= DMA_ATTR_SKIP_CPU_SYNC; > + } > + > __iommu_dma_unmap_swiotlb(dev, dma_handle, size, dir, attrs); Again, fold that into here and put the arch sync in an else case to the is_swiotlb_buffer() check. > } > > @@ -999,8 +1002,10 @@ static int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg, > if (dev_is_untrusted(dev)) > return iommu_dma_map_sg_swiotlb(dev, sg, nents, dir, attrs); > > - if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) > + if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) { > iommu_dma_sync_sg_for_device(dev, sg, nents, dir); > + attrs |= DMA_ATTR_SKIP_CPU_SYNC; > + } Why? attrs is never referenced again after this. > /* > * Work out how much IOVA space we need, and align the segments to > @@ -1068,8 +1073,10 @@ static void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, > struct scatterlist *tmp; > int i; > > - if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) > + if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) { > iommu_dma_sync_sg_for_cpu(dev, sg, nents, dir); > + attrs |= DMA_ATTR_SKIP_CPU_SYNC; > + } Just move it down so it's out of the SWIOTLB path entirely. Exactly like you did in patch #2 for map_sg, conspicuous in the hunk above. Robin. > > if (dev_is_untrusted(dev)) { > iommu_dma_unmap_sg_swiotlb(dev, sg, nents, dir, attrs); > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2021-08-11 19:00 UTC|newest] Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-08-11 2:42 [PATCH v3 0/5] Fixes for dma-iommu swiotlb bounce buffers David Stevens 2021-08-11 2:42 ` David Stevens 2021-08-11 2:42 ` [PATCH v3 1/5] dma-iommu: fix sync_sg with swiotlb David Stevens 2021-08-11 2:42 ` David Stevens 2021-08-11 5:57 ` Christoph Hellwig 2021-08-11 5:57 ` Christoph Hellwig 2021-08-11 18:22 ` Robin Murphy 2021-08-11 18:22 ` Robin Murphy 2021-08-11 2:42 ` [PATCH v3 2/5] dma-iommu: fix arch_sync_dma for map David Stevens 2021-08-11 2:42 ` David Stevens 2021-08-11 6:01 ` Christoph Hellwig 2021-08-11 6:01 ` Christoph Hellwig 2021-08-11 18:47 ` Robin Murphy 2021-08-11 18:47 ` Robin Murphy 2021-08-12 9:21 ` David Stevens 2021-08-12 9:21 ` David Stevens 2021-08-12 10:38 ` Robin Murphy 2021-08-12 10:38 ` Robin Murphy 2021-08-11 2:42 ` [PATCH v3 3/5] dma-iommu: add SKIP_CPU_SYNC after syncing David Stevens 2021-08-11 2:42 ` David Stevens 2021-08-11 6:07 ` Christoph Hellwig 2021-08-11 6:07 ` Christoph Hellwig 2021-08-11 19:00 ` Robin Murphy [this message] 2021-08-11 19:00 ` Robin Murphy 2021-08-11 2:42 ` [PATCH v3 4/5] dma-iommu: Check CONFIG_SWIOTLB more broadly David Stevens 2021-08-11 2:42 ` David Stevens 2021-08-11 19:02 ` Robin Murphy 2021-08-11 19:02 ` Robin Murphy 2021-08-11 2:42 ` [PATCH v3 5/5] dma-iommu: account for min_align_mask David Stevens 2021-08-11 2:42 ` David Stevens 2021-08-11 9:26 ` Mi, Dapeng1 2021-08-11 9:26 ` Mi, Dapeng1 2021-08-11 19:12 ` Robin Murphy 2021-08-11 19:12 ` Robin Murphy 2021-08-12 1:45 ` David Stevens 2021-08-12 1:45 ` David Stevens 2021-08-12 9:57 ` Robin Murphy 2021-08-12 9:57 ` Robin Murphy
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