From: Pranjal Shrivastava Date: Wed, 26 Nov 2025 11:41:12 +0000 (+0000) Subject: dma-direct: Fix missing sg_dma_len assignment in P2PDMA bus mappings X-Git-Tag: v6.18~16^2 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=d0d08f4bd7f667dc7a65cd7133c0a94a6f02aca3;p=thirdparty%2Flinux.git dma-direct: Fix missing sg_dma_len assignment in P2PDMA bus mappings Prior to commit a25e7962db0d7 ("PCI/P2PDMA: Refactor the p2pdma mapping helpers"), P2P segments were mapped using the pci_p2pdma_map_segment() helper. This helper was responsible for populating sg->dma_address, marking the bus address, and also setting sg_dma_len(sg). The refactor[1] removed this helper and moved the mapping logic directly into the callers. While iommu_dma_map_sg() was correctly updated to set the length in the new flow, it was missed in dma_direct_map_sg(). Thus, in dma_direct_map_sg(), the PCI_P2PDMA_MAP_BUS_ADDR case sets the dma_address and marks the segment, but immediately executes 'continue', which causes the loop to skip the standard assignment logic at the end: sg_dma_len(sg) = sg->length; As a result, when CONFIG_NEED_SG_DMA_LENGTH is enabled, the dma_length field remains uninitialized (zero) for P2P bus address mappings. This breaks upper-layer drivers (for e.g. RDMA/IB) that rely on sg_dma_len() to determine the transfer size. Fix this by explicitly setting the DMA length in the PCI_P2PDMA_MAP_BUS_ADDR case before continuing to the next scatterlist entry. Fixes: a25e7962db0d7 ("PCI/P2PDMA: Refactor the p2pdma mapping helpers") Reported-by: Jacob Moroni Signed-off-by: Pranjal Shrivastava [1] https://lore.kernel.org/all/ac14a0e94355bf898de65d023ccf8a2ad22a3ece.1746424934.git.leon@kernel.org/ Reviewed-by: Logan Gunthorpe Reviewed-by: Leon Romanovsky Reviewed-by: Shivaji Kant Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20251126114112.3694469-1-praan@google.com --- diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c index 1f9ee97594269..f973e7e73c90b 100644 --- a/kernel/dma/direct.c +++ b/kernel/dma/direct.c @@ -481,6 +481,7 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents, case PCI_P2PDMA_MAP_BUS_ADDR: sg->dma_address = pci_p2pdma_bus_addr_map(&p2pdma_state, sg_phys(sg)); + sg_dma_len(sg) = sg->length; sg_dma_mark_bus_address(sg); continue; default: