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https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson
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858299dc61
Add a new blk_rq_dma_map / blk_rq_dma_unmap pair that does away with the wasteful scatterlist structure. Instead it uses the mapping iterator to either add segments to the IOVA for IOMMU operations, or just maps them one by one for the direct mapping. For the IOMMU case instead of a scatterlist with an entry for each segment, only a single [dma_addr,len] pair needs to be stored for processing a request, and for the direct mapping the per-segment allocation shrinks from [page,offset,len,dma_addr,dma_len] to just [dma_addr,len]. One big difference to the scatterlist API, which could be considered downside, is that the IOVA collapsing only works when the driver sets a virt_boundary that matches the IOMMU granule. For NVMe this is done already so it works perfectly. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Leon Romanovsky <leonro@nvidia.com> Link: https://lore.kernel.org/r/20250625113531.522027-3-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
64 lines
1.7 KiB
C
64 lines
1.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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#ifndef BLK_MQ_DMA_H
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#define BLK_MQ_DMA_H
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#include <linux/blk-mq.h>
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#include <linux/pci-p2pdma.h>
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struct blk_dma_iter {
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/* Output address range for this iteration */
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dma_addr_t addr;
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u32 len;
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/* Status code. Only valid when blk_rq_dma_map_iter_* returned false */
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blk_status_t status;
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/* Internal to blk_rq_dma_map_iter_* */
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struct req_iterator iter;
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struct pci_p2pdma_map_state p2pdma;
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};
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bool blk_rq_dma_map_iter_start(struct request *req, struct device *dma_dev,
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struct dma_iova_state *state, struct blk_dma_iter *iter);
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bool blk_rq_dma_map_iter_next(struct request *req, struct device *dma_dev,
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struct dma_iova_state *state, struct blk_dma_iter *iter);
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/**
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* blk_rq_dma_map_coalesce - were all segments coalesced?
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* @state: DMA state to check
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*
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* Returns true if blk_rq_dma_map_iter_start coalesced all segments into a
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* single DMA range.
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*/
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static inline bool blk_rq_dma_map_coalesce(struct dma_iova_state *state)
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{
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return dma_use_iova(state);
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}
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/**
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* blk_rq_dma_unmap - try to DMA unmap a request
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* @req: request to unmap
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* @dma_dev: device to unmap from
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* @state: DMA IOVA state
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* @mapped_len: number of bytes to unmap
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*
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* Returns %false if the callers need to manually unmap every DMA segment
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* mapped using @iter or %true if no work is left to be done.
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*/
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static inline bool blk_rq_dma_unmap(struct request *req, struct device *dma_dev,
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struct dma_iova_state *state, size_t mapped_len)
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{
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if (req->cmd_flags & REQ_P2PDMA)
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return true;
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if (dma_use_iova(state)) {
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dma_iova_destroy(dma_dev, state, mapped_len, rq_dma_dir(req),
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0);
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return true;
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}
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return !dma_need_unmap(dma_dev);
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}
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#endif /* BLK_MQ_DMA_H */
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