bbff2f321a
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>
64 lines
1.2 KiB
C
64 lines
1.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* XDP user-space ring structure
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* Copyright(c) 2018 Intel Corporation.
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*/
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#include <linux/slab.h>
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#include "xsk_queue.h"
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void xskq_set_umem(struct xsk_queue *q, struct xdp_umem_props *umem_props)
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{
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if (!q)
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return;
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q->umem_props = *umem_props;
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}
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static u32 xskq_umem_get_ring_size(struct xsk_queue *q)
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{
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return sizeof(struct xdp_umem_ring) + q->nentries * sizeof(u64);
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}
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static u32 xskq_rxtx_get_ring_size(struct xsk_queue *q)
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{
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return sizeof(struct xdp_ring) + q->nentries * sizeof(struct xdp_desc);
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}
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struct xsk_queue *xskq_create(u32 nentries, bool umem_queue)
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{
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struct xsk_queue *q;
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gfp_t gfp_flags;
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size_t size;
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q = kzalloc(sizeof(*q), GFP_KERNEL);
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if (!q)
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return NULL;
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q->nentries = nentries;
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q->ring_mask = nentries - 1;
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gfp_flags = GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN |
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__GFP_COMP | __GFP_NORETRY;
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size = umem_queue ? xskq_umem_get_ring_size(q) :
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xskq_rxtx_get_ring_size(q);
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q->ring = (struct xdp_ring *)__get_free_pages(gfp_flags,
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get_order(size));
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if (!q->ring) {
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kfree(q);
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return NULL;
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}
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return q;
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}
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void xskq_destroy(struct xsk_queue *q)
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{
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if (!q)
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return;
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page_frag_free(q->ring);
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kfree(q);
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}
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