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Date: Tue, 24 Apr 2018 02:16:56 +0300
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Björn Töpel <bjorn.topel@...il.com>
Cc: magnus.karlsson@...el.com, alexander.h.duyck@...el.com,
alexander.duyck@...il.com, john.fastabend@...il.com, ast@...com,
brouer@...hat.com, willemdebruijn.kernel@...il.com,
daniel@...earbox.net, netdev@...r.kernel.org,
michael.lundkvist@...csson.com, jesse.brandeburg@...el.com,
anjali.singhai@...el.com, qi.z.zhang@...el.com
Subject: Re: [PATCH bpf-next 03/15] xsk: add umem fill queue support and mmap
On Mon, Apr 23, 2018 at 03:56:07PM +0200, Björn Töpel wrote:
> From: Magnus Karlsson <magnus.karlsson@...el.com>
>
> Here, we add another setsockopt for registered user memory (umem)
> called XDP_UMEM_FILL_QUEUE. Using this socket option, the process can
> ask the kernel to allocate a queue (ring buffer) and also mmap it
> (XDP_UMEM_PGOFF_FILL_QUEUE) into the process.
>
> The queue is used to explicitly pass ownership of umem frames from the
> user process to the kernel. These frames will in a later patch be
> filled in with Rx packet data by the kernel.
>
> Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>
> ---
> include/uapi/linux/if_xdp.h | 15 +++++++++++
> net/xdp/Makefile | 2 +-
> net/xdp/xdp_umem.c | 5 ++++
> net/xdp/xdp_umem.h | 2 ++
> net/xdp/xsk.c | 62 ++++++++++++++++++++++++++++++++++++++++++++-
> net/xdp/xsk_queue.c | 58 ++++++++++++++++++++++++++++++++++++++++++
> net/xdp/xsk_queue.h | 38 +++++++++++++++++++++++++++
> 7 files changed, 180 insertions(+), 2 deletions(-)
> create mode 100644 net/xdp/xsk_queue.c
> create mode 100644 net/xdp/xsk_queue.h
>
> diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h
> index 41252135a0fe..975661e1baca 100644
> --- a/include/uapi/linux/if_xdp.h
> +++ b/include/uapi/linux/if_xdp.h
> @@ -23,6 +23,7 @@
>
> /* XDP socket options */
> #define XDP_UMEM_REG 3
> +#define XDP_UMEM_FILL_RING 4
>
> struct xdp_umem_reg {
> __u64 addr; /* Start of packet data area */
> @@ -31,4 +32,18 @@ struct xdp_umem_reg {
> __u32 frame_headroom; /* Frame head room */
> };
>
> +/* Pgoff for mmaping the rings */
> +#define XDP_UMEM_PGOFF_FILL_RING 0x100000000
> +
> +struct xdp_ring {
> + __u32 producer __attribute__((aligned(64)));
> + __u32 consumer __attribute__((aligned(64)));
> +};
> +
> +/* Used for the fill and completion queues for buffers */
> +struct xdp_umem_ring {
> + struct xdp_ring ptrs;
> + __u32 desc[0] __attribute__((aligned(64)));
> +};
> +
> #endif /* _LINUX_IF_XDP_H */
> diff --git a/net/xdp/Makefile b/net/xdp/Makefile
> index a5d736640a0f..074fb2b2d51c 100644
> --- a/net/xdp/Makefile
> +++ b/net/xdp/Makefile
> @@ -1,2 +1,2 @@
> -obj-$(CONFIG_XDP_SOCKETS) += xsk.o xdp_umem.o
> +obj-$(CONFIG_XDP_SOCKETS) += xsk.o xdp_umem.o xsk_queue.o
>
> diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
> index bff058f5a769..6fc233e03f30 100644
> --- a/net/xdp/xdp_umem.c
> +++ b/net/xdp/xdp_umem.c
> @@ -62,6 +62,11 @@ static void xdp_umem_release(struct xdp_umem *umem)
> struct mm_struct *mm;
> unsigned long diff;
>
> + if (umem->fq) {
> + xskq_destroy(umem->fq);
> + umem->fq = NULL;
> + }
> +
> if (umem->pgs) {
> xdp_umem_unpin_pages(umem);
>
> diff --git a/net/xdp/xdp_umem.h b/net/xdp/xdp_umem.h
> index 58714f4f7f25..3086091aebdd 100644
> --- a/net/xdp/xdp_umem.h
> +++ b/net/xdp/xdp_umem.h
> @@ -18,9 +18,11 @@
> #include <linux/mm.h>
> #include <linux/if_xdp.h>
>
> +#include "xsk_queue.h"
> #include "xdp_umem_props.h"
>
> struct xdp_umem {
> + struct xsk_queue *fq;
> struct page **pgs;
> struct xdp_umem_props props;
> u32 npgs;
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index 19fc719cbe0d..bf6a1151df28 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -32,6 +32,7 @@
> #include <linux/netdevice.h>
> #include <net/sock.h>
>
> +#include "xsk_queue.h"
> #include "xdp_umem.h"
>
> struct xdp_sock {
> @@ -47,6 +48,21 @@ static struct xdp_sock *xdp_sk(struct sock *sk)
> return (struct xdp_sock *)sk;
> }
>
> +static int xsk_init_queue(u32 entries, struct xsk_queue **queue)
> +{
> + struct xsk_queue *q;
> +
> + if (entries == 0 || *queue || !is_power_of_2(entries))
> + return -EINVAL;
> +
> + q = xskq_create(entries);
> + if (!q)
> + return -ENOMEM;
> +
> + *queue = q;
> + return 0;
> +}
> +
> static int xsk_release(struct socket *sock)
> {
> struct sock *sk = sock->sk;
> @@ -109,6 +125,23 @@ static int xsk_setsockopt(struct socket *sock, int level, int optname,
> mutex_unlock(&xs->mutex);
> return 0;
> }
> + case XDP_UMEM_FILL_RING:
> + {
> + struct xsk_queue **q;
> + int entries;
> +
> + if (!xs->umem)
> + return -EINVAL;
> +
> + if (copy_from_user(&entries, optval, sizeof(entries)))
> + return -EFAULT;
> +
> + mutex_lock(&xs->mutex);
> + q = &xs->umem->fq;
> + err = xsk_init_queue(entries, q);
> + mutex_unlock(&xs->mutex);
> + return err;
> + }
> default:
> break;
> }
> @@ -116,6 +149,33 @@ static int xsk_setsockopt(struct socket *sock, int level, int optname,
> return -ENOPROTOOPT;
> }
>
> +static int xsk_mmap(struct file *file, struct socket *sock,
> + struct vm_area_struct *vma)
> +{
> + unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
> + unsigned long size = vma->vm_end - vma->vm_start;
> + struct xdp_sock *xs = xdp_sk(sock->sk);
> + struct xsk_queue *q;
> + unsigned long pfn;
> + struct page *qpg;
> +
> + if (!xs->umem)
> + return -EINVAL;
> +
> + if (offset == XDP_UMEM_PGOFF_FILL_RING)
> + q = xs->umem->fq;
> + else
> + return -EINVAL;
> +
> + qpg = virt_to_head_page(q->ring);
> + if (size > (PAGE_SIZE << compound_order(qpg)))
> + return -EINVAL;
> +
> + pfn = virt_to_phys(q->ring) >> PAGE_SHIFT;
> + return remap_pfn_range(vma, vma->vm_start, pfn,
> + size, vma->vm_page_prot);
> +}
> +
> static struct proto xsk_proto = {
> .name = "XDP",
> .owner = THIS_MODULE,
> @@ -139,7 +199,7 @@ static const struct proto_ops xsk_proto_ops = {
> .getsockopt = sock_no_getsockopt,
> .sendmsg = sock_no_sendmsg,
> .recvmsg = sock_no_recvmsg,
> - .mmap = sock_no_mmap,
> + .mmap = xsk_mmap,
> .sendpage = sock_no_sendpage,
> };
>
> diff --git a/net/xdp/xsk_queue.c b/net/xdp/xsk_queue.c
> new file mode 100644
> index 000000000000..23da4f29d3fb
> --- /dev/null
> +++ b/net/xdp/xsk_queue.c
> @@ -0,0 +1,58 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* XDP user-space ring structure
> + * Copyright(c) 2018 Intel Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
> + * more details.
> + */
> +
> +#include <linux/slab.h>
> +
> +#include "xsk_queue.h"
> +
> +static u32 xskq_umem_get_ring_size(struct xsk_queue *q)
> +{
> + return sizeof(struct xdp_umem_ring) + q->nentries * sizeof(u32);
> +}
> +
> +struct xsk_queue *xskq_create(u32 nentries)
> +{
> + struct xsk_queue *q;
> + gfp_t gfp_flags;
> + size_t size;
> +
> + q = kzalloc(sizeof(*q), GFP_KERNEL);
> + if (!q)
> + return NULL;
> +
> + q->nentries = nentries;
> + q->ring_mask = nentries - 1;
> +
> + gfp_flags = GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN |
> + __GFP_COMP | __GFP_NORETRY;
> + size = xskq_umem_get_ring_size(q);
> +
> + q->ring = (struct xdp_ring *)__get_free_pages(gfp_flags,
> + get_order(size));
> + if (!q->ring) {
> + kfree(q);
> + return NULL;
> + }
> +
> + return q;
> +}
> +
> +void xskq_destroy(struct xsk_queue *q)
> +{
> + if (!q)
> + return;
> +
> + page_frag_free(q->ring);
> + kfree(q);
> +}
> diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
> new file mode 100644
> index 000000000000..7eb556bf73be
> --- /dev/null
> +++ b/net/xdp/xsk_queue.h
> @@ -0,0 +1,38 @@
> +/* SPDX-License-Identifier: GPL-2.0
> + * XDP user-space ring structure
> + * Copyright(c) 2018 Intel Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
> + * more details.
> + */
> +
> +#ifndef _LINUX_XSK_QUEUE_H
> +#define _LINUX_XSK_QUEUE_H
> +
> +#include <linux/types.h>
> +#include <linux/if_xdp.h>
> +
> +#include "xdp_umem_props.h"
> +
> +struct xsk_queue {
> + struct xdp_umem_props umem_props;
> + u32 ring_mask;
> + u32 nentries;
> + u32 prod_head;
> + u32 prod_tail;
> + u32 cons_head;
> + u32 cons_tail;
> + struct xdp_ring *ring;
> + u64 invalid_descs;
> +};
Any documentation on how e.g. the locking works here?
> +
> +struct xsk_queue *xskq_create(u32 nentries);
> +void xskq_destroy(struct xsk_queue *q);
> +
> +#endif /* _LINUX_XSK_QUEUE_H */
> --
> 2.14.1
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