This type is required by iommufd and kvm as dmabuf importers. Due to sensitivity about abusing physical addresses, restrict importers by using EXPORT_SYMBOL_FOR_MODULES(). Only iommufd can implement an importer, the kernel module loader will enforce this.
Allow anything to implement an exporter as there are use cases in DPDK/SPDK to connect GPU memory into VFIO/iommufd and it is hard to abuse the API as an exporter. The physical address list exporter returns a physical address list in a simple kvalloc'd array of struct phys_vec. For now all entries are assumed to be MMIO and iommufd will map into the IOMMU using the IOMMU_MMIO flag. Signed-off-by: Jason Gunthorpe <[email protected]> --- drivers/dma-buf/dma-buf-mapping.c | 63 +++++++++++++++++++++++++++++++ include/linux/dma-buf-mapping.h | 42 +++++++++++++++++++++ 2 files changed, 105 insertions(+) diff --git a/drivers/dma-buf/dma-buf-mapping.c b/drivers/dma-buf/dma-buf-mapping.c index baa96b37e2c6bd..d9d6b9b5bf05c6 100644 --- a/drivers/dma-buf/dma-buf-mapping.c +++ b/drivers/dma-buf/dma-buf-mapping.c @@ -349,3 +349,66 @@ struct dma_buf_mapping_type dma_buf_mapping_sgt_type = { .debugfs_dump = dma_buf_sgt_debugfs_dump, }; EXPORT_SYMBOL_NS_GPL(dma_buf_mapping_sgt_type, "DMA_BUF"); + +static const struct dma_buf_mapping_pal_exp_ops * +to_pal_exp_ops(struct dma_buf_attachment *attach) +{ + return container_of(attach->map_type.exp_ops, + struct dma_buf_mapping_pal_exp_ops, ops); +} + +/** + * dma_buf_pal_map_phys - Obtain the physical address list for a PAL attachment + * @attach: The DMA-buf attachment + * + * Calls the exporter's map_phys() callback to retrieve the physical address + * list for the buffer. The caller must hold the dma-buf's reservation lock. + * + * This symbol is restricted to iommufd to prevent misuse. + * + * Returns the physical address list on success, or an ERR_PTR on failure. + * The returned list must be freed with dma_buf_pal_unmap_phys(). + */ +struct dma_buf_phys_list * +dma_buf_pal_map_phys(struct dma_buf_attachment *attach) +{ + dma_resv_assert_held(attach->dmabuf->resv); + return to_pal_exp_ops(attach)->map_phys(attach); +} +/* + * Restricted, iommufd is the only importer allowed to prevent misuse of this + * API. + */ +EXPORT_SYMBOL_FOR_MODULES(dma_buf_pal_map_phys, "iommufd"); + +/** + * dma_buf_pal_unmap_phys - Unmap a physical address list + * @attach: The DMA-buf attachment + * @phys: The physical address list returned by dma_buf_pal_map_phys() + * + * Returns the mapping back to the exporter. After this point the importer may + * not touch any of the addresses in any way. + */ +void dma_buf_pal_unmap_phys(struct dma_buf_attachment *attach, + struct dma_buf_phys_list *phys) +{ + to_pal_exp_ops(attach)->unmap_phys(attach, phys); +} +EXPORT_SYMBOL_NS_GPL(dma_buf_pal_unmap_phys, "DMA_BUF"); + +static inline void +dma_buf_pal_finish_match(struct dma_buf_match_args *args, + const struct dma_buf_mapping_match *exp, + const struct dma_buf_mapping_match *imp) +{ + args->attach->map_type = (struct dma_buf_mapping_match){ + .type = &dma_buf_mapping_pal_type, + .exp_ops = exp->exp_ops, + }; +} + +struct dma_buf_mapping_type dma_buf_mapping_pal_type = { + .name = "Physical Address List", + .finish_match = dma_buf_pal_finish_match, +}; +EXPORT_SYMBOL_NS_GPL(dma_buf_mapping_pal_type, "DMA_BUF"); diff --git a/include/linux/dma-buf-mapping.h b/include/linux/dma-buf-mapping.h index ac859b8913edcd..10831ce2e72851 100644 --- a/include/linux/dma-buf-mapping.h +++ b/include/linux/dma-buf-mapping.h @@ -269,4 +269,46 @@ DMA_BUF_EMAPPING_SGT_P2P(const struct dma_buf_mapping_sgt_exp_ops *exp_ops, .exporter_requires_p2p = DMA_SGT_NO_P2P, \ } }) +/* + * Physical Address List mapping type + * + * Use of the Physical Address List type is restricted to prevent abuse of the + * physical addresses API. Please check with the DMA BUF maintainers before + * trying to use it. + */ +struct dma_buf_phys_list { + size_t length; + struct dma_buf_phys_vec phys[] __counted_by(length); +}; + +extern struct dma_buf_mapping_type dma_buf_mapping_pal_type; + +struct dma_buf_mapping_pal_exp_ops { + struct dma_buf_mapping_exp_ops ops; + struct dma_buf_phys_list *(*map_phys)(struct dma_buf_attachment *attach); + void (*unmap_phys)(struct dma_buf_attachment *attach, + struct dma_buf_phys_list *phys); +}; + +struct dma_buf_phys_list * +dma_buf_pal_map_phys(struct dma_buf_attachment *attach); +void dma_buf_pal_unmap_phys(struct dma_buf_attachment *attach, + struct dma_buf_phys_list *phys); + +static inline struct dma_buf_mapping_match DMA_BUF_IMAPPING_PAL(void) +{ + return (struct dma_buf_mapping_match){ + .type = &dma_buf_mapping_pal_type, + }; +} + +static inline struct dma_buf_mapping_match +DMA_BUF_EMAPPING_PAL(const struct dma_buf_mapping_pal_exp_ops *exp_ops) +{ + return (struct dma_buf_mapping_match){ + .type = &dma_buf_mapping_pal_type, + .exp_ops = &exp_ops->ops, + }; +} + #endif -- 2.43.0
