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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 <bjorn.topel@intel.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
43 lines
948 B
C
43 lines
948 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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/* XDP user-space packet buffer
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* Copyright(c) 2018 Intel Corporation.
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*/
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#ifndef XDP_UMEM_H_
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#define XDP_UMEM_H_
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#include <linux/mm.h>
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#include <linux/if_xdp.h>
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#include <linux/workqueue.h>
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#include "xsk_queue.h"
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#include "xdp_umem_props.h"
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struct xdp_umem {
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struct xsk_queue *fq;
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struct xsk_queue *cq;
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struct page **pgs;
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struct xdp_umem_props props;
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u32 headroom;
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u32 chunk_size_nohr;
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struct user_struct *user;
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struct pid *pid;
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unsigned long address;
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refcount_t users;
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struct work_struct work;
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u32 npgs;
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};
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static inline char *xdp_umem_get_data(struct xdp_umem *umem, u64 addr)
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{
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return page_address(umem->pgs[addr >> PAGE_SHIFT]) +
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(addr & (PAGE_SIZE - 1));
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}
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bool xdp_umem_validate_queues(struct xdp_umem *umem);
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void xdp_get_umem(struct xdp_umem *umem);
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void xdp_put_umem(struct xdp_umem *umem);
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struct xdp_umem *xdp_umem_create(struct xdp_umem_reg *mr);
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#endif /* XDP_UMEM_H_ */
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