Hi, here is the fourth version of this patch-set. Previous versions can be found here: V1: https://lore.kernel.org/lkml/20190110134433.15672-1-joro@xxxxxxxxxx/ V2: https://lore.kernel.org/lkml/20190115132257.6426-1-joro@xxxxxxxxxx/ V3: https://lore.kernel.org/lkml/20190123163049.24863-1-joro@xxxxxxxxxx/ The problem solved here is a limitation of the SWIOTLB implementation, which does not support allocations larger than 256kb. When the virtio-blk driver tries to read/write a block larger than that, the allocation of the dma-handle fails and an IO error is reported. For all changes to v3, a diff to v3 of the patch-set is at the end of this email. Please review. Thanks, Joerg Joerg Roedel (5): swiotlb: Introduce swiotlb_max_mapping_size() swiotlb: Add is_swiotlb_active() function dma: Introduce dma_max_mapping_size() virtio: Introduce virtio_max_dma_size() virtio-blk: Consider virtio_max_dma_size() for maximum segment size Documentation/DMA-API.txt | 8 ++++++++ drivers/block/virtio_blk.c | 10 ++++++---- drivers/virtio/virtio_ring.c | 10 ++++++++++ include/linux/dma-mapping.h | 16 ++++++++++++++++ include/linux/swiotlb.h | 11 +++++++++++ include/linux/virtio.h | 2 ++ kernel/dma/direct.c | 11 +++++++++++ kernel/dma/swiotlb.c | 14 ++++++++++++++ 8 files changed, 78 insertions(+), 4 deletions(-) -- 2.17.1 diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt index e133ccd60228..acfe3d0f78d1 100644 --- a/Documentation/DMA-API.txt +++ b/Documentation/DMA-API.txt @@ -195,6 +195,14 @@ Requesting the required mask does not alter the current mask. If you wish to take advantage of it, you should issue a dma_set_mask() call to set the mask to the value returned. +:: + + size_t + dma_direct_max_mapping_size(struct device *dev); + +Returns the maximum size of a mapping for the device. The size parameter +of the mapping functions like dma_map_single(), dma_map_page() and +others should not be larger than the returned value. Part Id - Streaming DMA mappings -------------------------------- diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h index 5c087d330b4b..e9e786b4b598 100644 --- a/include/linux/swiotlb.h +++ b/include/linux/swiotlb.h @@ -62,7 +62,7 @@ extern void swiotlb_tbl_sync_single(struct device *hwdev, extern int swiotlb_dma_supported(struct device *hwdev, u64 mask); -extern size_t swiotlb_max_mapping_size(struct device *dev); +size_t swiotlb_max_mapping_size(struct device *dev); bool is_swiotlb_active(void); #ifdef CONFIG_SWIOTLB diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index 9fbd075081d9..c873f9cc2146 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -670,5 +670,9 @@ size_t swiotlb_max_mapping_size(struct device *dev) bool is_swiotlb_active(void) { - return !no_iotlb_memory; + /* + * When SWIOTLB is initialized, even if io_tlb_start points to physical + * address zero, io_tlb_end surely doesn't. + */ + return io_tlb_end != 0; }
