From bbff2f321a864ee07c9d3d1245af498023146951 Mon Sep 17 00:00:00 2001 From: Björn Töpel Date: Mon, 4 Jun 2018 13:57:13 +0200 Subject: xsk: new descriptor addressing scheme MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Currently, AF_XDP only supports a fixed frame-size memory scheme where each frame is referenced via an index (idx). A user passes the frame index to the kernel, and the kernel acts upon the data. Some NICs, however, do not have a fixed frame-size model, instead they have a model where a memory window is passed to the hardware and multiple frames are filled into that window (referred to as the "type-writer" model). By changing the descriptor format from the current frame index addressing scheme, AF_XDP can in the future be extended to support these kinds of NICs. In the index-based model, an idx refers to a frame of size frame_size. Addressing a frame in the UMEM is done by offseting the UMEM starting address by a global offset, idx * frame_size + offset. Communicating via the fill- and completion-rings are done by means of idx. In this commit, the idx is removed in favor of an address (addr), which is a relative address ranging over the UMEM. To convert an idx-based address to the new addr is simply: addr = idx * frame_size + offset. We also stop referring to the UMEM "frame" as a frame. Instead it is simply called a chunk. To transfer ownership of a chunk to the kernel, the addr of the chunk is passed in the fill-ring. Note, that the kernel will mask addr to make it chunk aligned, so there is no need for userspace to do that. E.g., for a chunk size of 2k, passing an addr of 2048, 2050 or 3000 to the fill-ring will refer to the same chunk. On the completion-ring, the addr will match that of the Tx descriptor, passed to the kernel. Changing the descriptor format to use chunks/addr will allow for future changes to move to a type-writer based model, where multiple frames can reside in one chunk. In this model passing one single chunk into the fill-ring, would potentially result in multiple Rx descriptors. This commit changes the uapi of AF_XDP sockets, and updates the documentation. Signed-off-by: Björn Töpel Signed-off-by: Daniel Borkmann --- net/xdp/xdp_umem.h | 27 ++++++--------------------- 1 file changed, 6 insertions(+), 21 deletions(-) (limited to 'net/xdp/xdp_umem.h') diff --git a/net/xdp/xdp_umem.h b/net/xdp/xdp_umem.h index 0881cf456230..aeadd1bcb72d 100644 --- a/net/xdp/xdp_umem.h +++ b/net/xdp/xdp_umem.h @@ -18,35 +18,20 @@ struct xdp_umem { struct xsk_queue *cq; struct page **pgs; struct xdp_umem_props props; - u32 npgs; - u32 frame_headroom; - u32 nfpp_mask; - u32 nfpplog2; - u32 frame_size_log2; + u32 headroom; + u32 chunk_size_nohr; struct user_struct *user; struct pid *pid; unsigned long address; - size_t size; refcount_t users; struct work_struct work; + u32 npgs; }; -static inline char *xdp_umem_get_data(struct xdp_umem *umem, u32 idx) -{ - u64 pg, off; - char *data; - - pg = idx >> umem->nfpplog2; - off = (idx & umem->nfpp_mask) << umem->frame_size_log2; - - data = page_address(umem->pgs[pg]); - return data + off; -} - -static inline char *xdp_umem_get_data_with_headroom(struct xdp_umem *umem, - u32 idx) +static inline char *xdp_umem_get_data(struct xdp_umem *umem, u64 addr) { - return xdp_umem_get_data(umem, idx) + umem->frame_headroom; + return page_address(umem->pgs[addr >> PAGE_SHIFT]) + + (addr & (PAGE_SIZE - 1)); } bool xdp_umem_validate_queues(struct xdp_umem *umem); -- cgit v1.2.3-59-g8ed1b