xsk: add umem fill queue support and mmap

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.

v2: Fixed potential crash in xsk_mmap.

Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 58 insertions, 0 deletions

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);
+}