[PATCH v5 13/15] iommu/dma: Force bouncing if the size is not cacheline-aligned
Jisheng Zhang
jszhang at kernel.org
Fri May 26 09:36:30 PDT 2023
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 at arm.com>
> Cc: Joerg Roedel <joro at 8bytes.org>
> Cc: Christoph Hellwig <hch at lst.de>
> Cc: Robin Murphy <robin.murphy at arm.com>
> ---
> 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
>
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