From: Alex Mastro Date: Wed, 10 Jun 2026 20:44:41 +0000 (-0700) Subject: iommufd: Clarify IOAS_MAP_FILE dma-buf support X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=298ab7e6f1637cec44163f52e84e2030ec16ed9d;p=thirdparty%2Fkernel%2Flinux.git iommufd: Clarify IOAS_MAP_FILE dma-buf support IOMMU_IOAS_MAP_FILE is documented as mapping a memfd, but the implementation first tries to resolve the fd as a dma-buf and has a special path for supported dma-buf exporters. In particular, VFIO PCI dma-bufs exported through VFIO_DEVICE_FEATURE_DMA_BUF can be mapped when they describe a single DMA range. Update the UAPI comment so userspace understands that certain kinds of dma-buf are supported in addition to memfd. Fixes: 44ebaa1744fd ("iommufd: Accept a DMABUF through IOMMU_IOAS_MAP_FILE") Link: https://patch.msgid.link/r/20260610-tmp-v1-1-b8ccbf557391@fb.com Signed-off-by: Alex Mastro Assisted-by: Codex:gpt-5.5-high Signed-off-by: Jason Gunthorpe --- diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h index e998dfbd69603..0425d452d41ed 100644 --- a/include/uapi/linux/iommufd.h +++ b/include/uapi/linux/iommufd.h @@ -224,13 +224,17 @@ struct iommu_ioas_map { * @size: sizeof(struct iommu_ioas_map_file) * @flags: same as for iommu_ioas_map * @ioas_id: same as for iommu_ioas_map - * @fd: the memfd to map - * @start: byte offset from start of file to map from + * @fd: the memfd or supported dma-buf file to map + * @start: byte offset from start of the file to map from * @length: same as for iommu_ioas_map * @iova: same as for iommu_ioas_map * - * Set an IOVA mapping from a memfd file. All other arguments and semantics - * match those of IOMMU_IOAS_MAP. + * Set an IOVA mapping from a memfd file. On kernels with dma-buf support, + * supported dma-buf files may also be accepted. This is not a generic + * dma-buf import path; currently supported dma-bufs include single-range + * VFIO PCI dma-bufs exported through VFIO_DEVICE_FEATURE_DMA_BUF, and + * other dma-bufs may be rejected. All other arguments and semantics match + * those of IOMMU_IOAS_MAP. */ struct iommu_ioas_map_file { __u32 size;