netdev - [RFC PATCH v2 10/14] xsk: add umem completion queue support and mmap

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Date:   Tue, 27 Mar 2018 18:59:15 +0200
From:   Björn Töpel <bjorn.topel@...il.com>
To:     bjorn.topel@...il.com, 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
Cc:     michael.lundkvist@...csson.com, jesse.brandeburg@...el.com,
        anjali.singhai@...el.com, qi.z.zhang@...el.com,
        ravineet.singh@...csson.com
Subject: [RFC PATCH v2 10/14] xsk: add umem completion queue support and mmap

From: Magnus Karlsson <magnus.karlsson@...el.com>

Here, we add another setsockopt for registered user memory (umem)
called XDP_UMEM_COMPLETION_QUEUE. Using this socket option, the
process can ask the kernel to allocate a queue (ring buffer) and also
mmap it (XDP_UMEM_PGOFF_COMPLETION_QUEUE) into the process.

The queue is used to explicitly pass ownership of umem frames from the
kernel to user process. This will be used by the TX path to tell user
space that a certain frame has been transmitted and user space can use
it for something else, if it wishes.

Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>
---
 include/uapi/linux/if_xdp.h | 2 ++
 net/xdp/xdp_umem.c          | 7 ++++++-
 net/xdp/xdp_umem.h          | 1 +
 net/xdp/xsk.c               | 6 +++++-
 4 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h
index e3593df7323c..aec2eee4e751 100644
--- a/include/uapi/linux/if_xdp.h
+++ b/include/uapi/linux/if_xdp.h
@@ -35,6 +35,7 @@ struct sockaddr_xdp {
 #define XDP_RX_QUEUE		  1
 #define XDP_UMEM_REG		  3
 #define XDP_UMEM_FILL_QUEUE	  4
+#define XDP_UMEM_COMPLETION_QUEUE 5
 
 struct xdp_umem_reg {
 	__u64 addr; /* Start of packet data area */
@@ -46,6 +47,7 @@ struct xdp_umem_reg {
 /* Pgoff for mmaping the rings */
 #define XDP_PGOFF_RX_QUEUE			  0
 #define XDP_UMEM_PGOFF_FILL_QUEUE	0x100000000
+#define XDP_UMEM_PGOFF_COMPLETION_QUEUE 0x180000000
 
 struct xdp_desc {
 	__u32 idx;
diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index 96395beb980e..8912022d22ee 100644
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -71,6 +71,11 @@ static void xdp_umem_release(struct xdp_umem *umem)
 		umem->fq = NULL;
 	}
 
+	if (umem->cq) {
+		xskq_destroy(umem->cq);
+		umem->cq = NULL;
+	}
+
 	if (umem->pgs) {
 		xdp_umem_unpin_pages(umem);
 
@@ -250,5 +255,5 @@ int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 
 bool xdp_umem_validate_queues(struct xdp_umem *umem)
 {
-	return umem->fq;
+	return (umem->fq && umem->cq);
 }
diff --git a/net/xdp/xdp_umem.h b/net/xdp/xdp_umem.h
index 5e7105b7760b..3eda63797516 100644
--- a/net/xdp/xdp_umem.h
+++ b/net/xdp/xdp_umem.h
@@ -23,6 +23,7 @@
 
 struct xdp_umem {
 	struct xsk_queue *fq;
+	struct xsk_queue *cq;
 	struct pid *pid;
 	struct page **pgs;
 	unsigned long address;
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index a60b1fcfb2b3..2071365c39b1 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -347,6 +347,7 @@ static int xsk_setsockopt(struct socket *sock, int level, int optname,
 		return 0;
 	}
 	case XDP_UMEM_FILL_QUEUE:
+	case XDP_UMEM_COMPLETION_QUEUE:
 	{
 		struct xsk_queue **q;
 		int entries;
@@ -358,7 +359,8 @@ static int xsk_setsockopt(struct socket *sock, int level, int optname,
 			return -EFAULT;
 
 		mutex_lock(&xs->mutex);
-		q = &xs->umem->fq;
+		q = (optname == XDP_UMEM_FILL_QUEUE) ? &xs->umem->fq :
+			&xs->umem->cq;
 		err = xsk_init_queue(entries, q, true);
 		mutex_unlock(&xs->mutex);
 		return err;
@@ -389,6 +391,8 @@ static int xsk_mmap(struct file *file, struct socket *sock,
 
 		if (offset == XDP_UMEM_PGOFF_FILL_QUEUE)
 			q = xs->umem->fq;
+		else if (offset == XDP_UMEM_PGOFF_COMPLETION_QUEUE)
+			q = xs->umem->cq;
 		else
 			return -EINVAL;
 	}
-- 
2.14.1