On Wed, May 24, 2023 at 06:19:02PM +0100, Catalin Marinas wrote: > Similarly to the direct DMA, bounce small allocations as they may have > originated from a kmalloc() cache not safe for DMA. Unlike the direct > DMA, iommu_dma_map_sg() cannot call iommu_dma_map_sg_swiotlb() for all > non-coherent devices as this would break some cases where the iova is > expected to be contiguous (dmabuf). Instead, scan the scatterlist for > any small sizes and only go the swiotlb path if any element of the list > needs bouncing (note that iommu_dma_map_page() would still only bounce > those buffers which are not DMA-aligned). > > To avoid scanning the scatterlist on the 'sync' operations, introduce an > SG_DMA_USE_SWIOTLB flag set by iommu_dma_map_sg_swiotlb(). The > dev_use_swiotlb() function together with the newly added > dev_use_sg_swiotlb() now check for both untrusted devices and unaligned > kmalloc() buffers (suggested by Robin Murphy). > > Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> > Cc: Joerg Roedel <joro@xxxxxxxxxx> > Cc: Christoph Hellwig <hch@xxxxxx> > Cc: Robin Murphy <robin.murphy@xxxxxxx> > --- > drivers/iommu/Kconfig | 1 + > drivers/iommu/dma-iommu.c | 50 ++++++++++++++++++++++++++++++------- > include/linux/scatterlist.h | 25 +++++++++++++++++-- > 3 files changed, 65 insertions(+), 11 deletions(-) > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > index db98c3f86e8c..670eff7a8e11 100644 > --- a/drivers/iommu/Kconfig > +++ b/drivers/iommu/Kconfig > @@ -152,6 +152,7 @@ config IOMMU_DMA > select IOMMU_IOVA > select IRQ_MSI_IOMMU > select NEED_SG_DMA_LENGTH > + select NEED_SG_DMA_FLAGS if SWIOTLB > > # Shared Virtual Addressing > config IOMMU_SVA > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index 7a9f0b0bddbd..24a8b8c2368c 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -520,9 +520,38 @@ static bool dev_is_untrusted(struct device *dev) > return dev_is_pci(dev) && to_pci_dev(dev)->untrusted; > } > > -static bool dev_use_swiotlb(struct device *dev) > +static bool dev_use_swiotlb(struct device *dev, size_t size, > + enum dma_data_direction dir) > { > - return IS_ENABLED(CONFIG_SWIOTLB) && dev_is_untrusted(dev); > + return IS_ENABLED(CONFIG_SWIOTLB) && > + (dev_is_untrusted(dev) || > + dma_kmalloc_needs_bounce(dev, size, dir)); > +} > + > +static bool dev_use_sg_swiotlb(struct device *dev, struct scatterlist *sg, > + int nents, enum dma_data_direction dir) > +{ > + struct scatterlist *s; > + int i; > + > + if (!IS_ENABLED(CONFIG_SWIOTLB)) > + return false; > + > + if (dev_is_untrusted(dev)) > + return true; > + > + /* > + * If kmalloc() buffers are not DMA-safe for this device and > + * direction, check the individual lengths in the sg list. If any > + * element is deemed unsafe, use the swiotlb for bouncing. > + */ > + if (!dma_kmalloc_safe(dev, dir)) { > + for_each_sg(sg, s, nents, i) > + if (!dma_kmalloc_size_aligned(s->length)) > + return true; > + } > + > + return false; > } > > /** > @@ -922,7 +951,7 @@ static void iommu_dma_sync_single_for_cpu(struct device *dev, > { > phys_addr_t phys; > > - if (dev_is_dma_coherent(dev) && !dev_use_swiotlb(dev)) > + if (dev_is_dma_coherent(dev) && !dev_use_swiotlb(dev, size, dir)) > return; > > phys = iommu_iova_to_phys(iommu_get_dma_domain(dev), dma_handle); > @@ -938,7 +967,7 @@ static void iommu_dma_sync_single_for_device(struct device *dev, > { > phys_addr_t phys; > > - if (dev_is_dma_coherent(dev) && !dev_use_swiotlb(dev)) > + if (dev_is_dma_coherent(dev) && !dev_use_swiotlb(dev, size, dir)) > return; > > phys = iommu_iova_to_phys(iommu_get_dma_domain(dev), dma_handle); > @@ -956,7 +985,7 @@ static void iommu_dma_sync_sg_for_cpu(struct device *dev, > struct scatterlist *sg; > int i; > > - if (dev_use_swiotlb(dev)) > + if (sg_is_dma_use_swiotlb(sgl)) > for_each_sg(sgl, sg, nelems, i) > iommu_dma_sync_single_for_cpu(dev, sg_dma_address(sg), > sg->length, dir); > @@ -972,7 +1001,7 @@ static void iommu_dma_sync_sg_for_device(struct device *dev, > struct scatterlist *sg; > int i; > > - if (dev_use_swiotlb(dev)) > + if (sg_is_dma_use_swiotlb(sgl)) > for_each_sg(sgl, sg, nelems, i) > iommu_dma_sync_single_for_device(dev, > sg_dma_address(sg), > @@ -998,7 +1027,8 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page, > * If both the physical buffer start address and size are > * page aligned, we don't need to use a bounce page. > */ > - if (dev_use_swiotlb(dev) && iova_offset(iovad, phys | size)) { > + if (dev_use_swiotlb(dev, size, dir) && > + iova_offset(iovad, phys | size)) { > void *padding_start; > size_t padding_size, aligned_size; > > @@ -1166,6 +1196,8 @@ static int iommu_dma_map_sg_swiotlb(struct device *dev, struct scatterlist *sg, > struct scatterlist *s; > int i; > > + sg_dma_mark_use_swiotlb(sg); > + > for_each_sg(sg, s, nents, i) { > sg_dma_address(s) = iommu_dma_map_page(dev, sg_page(s), > s->offset, s->length, dir, attrs); > @@ -1210,7 +1242,7 @@ static int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg, > goto out; > } > > - if (dev_use_swiotlb(dev)) > + if (dev_use_sg_swiotlb(dev, sg, nents, dir)) > return iommu_dma_map_sg_swiotlb(dev, sg, nents, dir, attrs); > > if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) > @@ -1315,7 +1347,7 @@ static void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, > struct scatterlist *tmp; > int i; > > - if (dev_use_swiotlb(dev)) { > + if (sg_is_dma_use_swiotlb(sg)) { > iommu_dma_unmap_sg_swiotlb(dev, sg, nents, dir, attrs); > return; > } > diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h > index 87aaf8b5cdb4..330a157c5501 100644 > --- a/include/linux/scatterlist.h > +++ b/include/linux/scatterlist.h > @@ -248,6 +248,29 @@ static inline void sg_unmark_end(struct scatterlist *sg) > sg->page_link &= ~SG_END; > } > > +#define SG_DMA_BUS_ADDRESS (1 << 0) > +#define SG_DMA_USE_SWIOTLB (1 << 1) > + > +#ifdef CONFIG_SWIOTLB s/CONFIG_SWIOTLB/CONFIG_NEED_SG_DMA_FLAGS ? Otherwise, there's compiler error if SWIOTLB=y but IOMMU=n Thanks > +static inline bool sg_is_dma_use_swiotlb(struct scatterlist *sg) > +{ > + return sg->dma_flags & SG_DMA_USE_SWIOTLB; > +} > + > +static inline void sg_dma_mark_use_swiotlb(struct scatterlist *sg) > +{ > + sg->dma_flags |= SG_DMA_USE_SWIOTLB; > +} > +#else > +static inline bool sg_is_dma_use_swiotlb(struct scatterlist *sg) > +{ > + return false; > +} > +static inline void sg_dma_mark_use_swiotlb(struct scatterlist *sg) > +{ > +} > +#endif > + > /* > * CONFIG_PCI_P2PDMA depends on CONFIG_64BIT which means there is 4 bytes > * in struct scatterlist (assuming also CONFIG_NEED_SG_DMA_LENGTH is set). > @@ -256,8 +279,6 @@ static inline void sg_unmark_end(struct scatterlist *sg) > */ > #ifdef CONFIG_PCI_P2PDMA > > -#define SG_DMA_BUS_ADDRESS (1 << 0) > - > /** > * sg_dma_is_bus address - Return whether a given segment was marked > * as a bus address > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel