xsk: Introduce AF_XDP buffer allocation API

In order to simplify AF_XDP zero-copy enablement for NIC driver
developers, a new AF_XDP buffer allocation API is added. The
implementation is based on a single core (single producer/consumer)
buffer pool for the AF_XDP UMEM.

A buffer is allocated using the xsk_buff_alloc() function, and
returned using xsk_buff_free(). If a buffer is disassociated with the
pool, e.g. when a buffer is passed to an AF_XDP socket, a buffer is
said to be released. Currently, the release function is only used by
the AF_XDP internals and not visible to the driver.

Drivers using this API should register the XDP memory model with the
new MEM_TYPE_XSK_BUFF_POOL type.

The API is defined in net/xdp_sock_drv.h.

The buffer type is struct xdp_buff, and follows the lifetime of
regular xdp_buffs, i.e.  the lifetime of an xdp_buff is restricted to
a NAPI context. In other words, the API is not replacing xdp_frames.

In addition to introducing the API and implementations, the AF_XDP
core is migrated to use the new APIs.

rfc->v1: Fixed build errors/warnings for m68k and riscv. (kbuild test
         robot)
         Added headroom/chunk size getter. (Maxim/Björn)

v1->v2: Swapped SoBs. (Maxim)

v2->v3: Initialize struct xdp_buff member frame_sz. (Björn)
        Add API to query the DMA address of a frame. (Maxim)
        Do DMA sync for CPU till the end of the frame to handle
        possible growth (frame_sz). (Maxim)

Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200520192103.355233-6-bjorn.topel@gmail.com

1 files changed, 2 insertions, 0 deletions

diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
index fb7fe3060175..6e7265f63c04 100644
--- a/include/net/xdp_sock.h
+++ b/include/net/xdp_sock.h
@@ -31,11 +31,13 @@ struct xdp_umem_fq_reuse {
 struct xdp_umem {
 	struct xsk_queue *fq;
 	struct xsk_queue *cq;
+	struct xsk_buff_pool *pool;
 	struct xdp_umem_page *pages;
 	u64 chunk_mask;
 	u64 size;
 	u32 headroom;
 	u32 chunk_size_nohr;
+	u32 chunk_size;
 	struct user_struct *user;
 	refcount_t users;
 	struct work_struct work;