[PATCH v9 01/13] dma-buf: introduce initial file I/O infrastructure

[Pavel Begunkov]

On 10/12/26 14:08, Matthew Brost wrote:
> On Wed, Oct 07, 2026 at 02:42:44AM +0100, Pavel Begunkov wrote:
>> The goal is to be able to natively use dma-buf in the read-write / IO
>> path. This patch adds basic building blocks serving as a glue and API
>> between drivers and upper layer subsystems providing the uAPI. Later
>> patches implement it for NVMe raw block devices and expose it to the
>> user space via io_uring.
>>
>> There are two main objects. struct dma_buf_io_ctx and struct
>> dma_buf_io_map. The ctx is used during initial registration and serves
>> as an interface between the upper layer user like io_uring and to the
>> importer subsystem / driver. The map represents the actual dma map
>> established for the target device[s] with dma_buf_map_attachment() and
>> stored in a device specific format. The context is created via a new
>> file operation ->init_dma_buf_io_ctx.
>>
>> The ctx-map separation exists to facilitate map invalidation (see
>> dma_buf_io_invalidate_mappings()). A ctx can create
>> multiple maps during its lifetime, but there can only be no more than
>> one (active) map attached to it. Invalidation drops the active map
>> if present, and any new I/O request will try to create a new one.
>>
>> The primary task of dma_buf_io_map is to count requests using it
>> and wait for their completion when we want to destroy the DMA map.
>>
>> [un]mapping and any work with dma addresses is delegated to the
>> importer driver via an ops table stored in the ctx, see struct
>> dma_buf_io_ops. Only the target driver / subsystem knows about devices
>> it wants to use the dma-buf with, especially in case of multi-device
>> filesystems or stacking in the future.
>>
> 
> Full disclosure Pavel incorporated some of my ideas wrt to locking
> cleanup which I shared off the list.
> 
> So I can't in fairness give an RB but:
> Acked-by: Matthew Brost <matthew.brost at intel.com>
> 
> For the series - I can give this and I have pulled to code + have Xe
> nvme + IGT setup showing this working:
> 
> Tested-by: Matthew Brost <matthew.brost at intel.com>

Thanks for the suggestions and testing!

-- 
Pavel Begunkov