[PATCH net-next v1 08/19] virtio_net: sq support premapped mode

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

If the xsk is enabling, the xsk tx will share the send queue.
But the xsk requires that the send queue use the premapped mode.
So the send queue must support premapped mode.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
 drivers/net/virtio/main.c       | 108 ++++++++++++++++++++++++++++----
 drivers/net/virtio/virtio_net.h |  54 +++++++++++++++-
 2 files changed, 149 insertions(+), 13 deletions(-)

diff --git a/drivers/net/virtio/main.c b/drivers/net/virtio/main.c
index 8da84ea9bcbe..02d27101fef1 100644
--- a/drivers/net/virtio/main.c
+++ b/drivers/net/virtio/main.c
@@ -514,20 +514,104 @@ static void *virtnet_rq_alloc(struct virtnet_rq *rq, u32 size, gfp_t gfp)
 	return buf;
 }
 
-static void virtnet_rq_set_premapped(struct virtnet_info *vi)
+static int virtnet_sq_set_premapped(struct virtnet_sq *sq)
 {
-	int i;
+	struct virtnet_sq_dma *d;
+	int err, size, i;
 
-	/* disable for big mode */
-	if (!vi->mergeable_rx_bufs && vi->big_packets)
-		return;
+	size = virtqueue_get_vring_size(sq->vq);
+
+	size += MAX_SKB_FRAGS + 2;
+
+	sq->dmainfo.head = kcalloc(size, sizeof(*sq->dmainfo.head), GFP_KERNEL);
+	if (!sq->dmainfo.head)
+		return -ENOMEM;
+
+	err = virtqueue_set_dma_premapped(sq->vq);
+	if (err) {
+		kfree(sq->dmainfo.head);
+		return err;
+	}
+
+	sq->dmainfo.free = NULL;
+
+	sq->do_dma = true;
+
+	for (i = 0; i < size; ++i) {
+		d = &sq->dmainfo.head[i];
+
+		d->next = sq->dmainfo.free;
+		sq->dmainfo.free = d;
+	}
+
+	return 0;
+}
+
+static void virtnet_set_premapped(struct virtnet_info *vi)
+{
+	int i;
 
 	for (i = 0; i < vi->max_queue_pairs; i++) {
-		if (virtqueue_set_dma_premapped(vi->rq[i].vq))
+		if (!virtnet_sq_set_premapped(&vi->sq[i]))
+			vi->sq[i].do_dma = true;
+
+		/* disable for big mode */
+		if (!vi->mergeable_rx_bufs && vi->big_packets)
 			continue;
 
-		vi->rq[i].do_dma = true;
+		if (!virtqueue_set_dma_premapped(vi->rq[i].vq))
+			vi->rq[i].do_dma = true;
+	}
+}
+
+static struct virtnet_sq_dma *virtnet_sq_map_sg(struct virtnet_sq *sq, int nents, void *data)
+{
+	struct virtnet_sq_dma *d, *head;
+	struct scatterlist *sg;
+	int i;
+
+	head = NULL;
+
+	for_each_sg(sq->sg, sg, nents, i) {
+		sg->dma_address = virtqueue_dma_map_single_attrs(sq->vq, sg_virt(sg),
+								 sg->length,
+								 DMA_TO_DEVICE, 0);
+		if (virtqueue_dma_mapping_error(sq->vq, sg->dma_address))
+			goto err;
+
+		d = sq->dmainfo.free;
+		sq->dmainfo.free = d->next;
+
+		d->addr = sg->dma_address;
+		d->len = sg->length;
+
+		d->next = head;
+		head = d;
+	}
+
+	head->data = data;
+
+	return (void *)((unsigned long)head | ((unsigned long)data & VIRTIO_XMIT_DATA_MASK));
+err:
+	virtnet_sq_unmap(sq, head);
+	return NULL;
+}
+
+static int virtnet_add_outbuf(struct virtnet_sq *sq, u32 num, void *data)
+{
+	int ret;
+
+	if (sq->do_dma) {
+		data = virtnet_sq_map_sg(sq, num, data);
+		if (!data)
+			return -ENOMEM;
 	}
+
+	ret = virtqueue_add_outbuf(sq->vq, sq->sg, num, data, GFP_ATOMIC);
+	if (ret && sq->do_dma)
+		virtnet_sq_unmap(sq, data);
+
+	return ret;
 }
 
 static void free_old_xmit(struct virtnet_sq *sq, bool in_napi)
@@ -623,8 +707,7 @@ static int __virtnet_xdp_xmit_one(struct virtnet_info *vi,
 			    skb_frag_size(frag), skb_frag_off(frag));
 	}
 
-	err = virtqueue_add_outbuf(sq->vq, sq->sg, nr_frags + 1,
-				   xdp_to_ptr(xdpf), GFP_ATOMIC);
+	err = virtnet_add_outbuf(sq, nr_frags + 1, xdp_to_ptr(xdpf));
 	if (unlikely(err))
 		return -ENOSPC; /* Caller handle free/refcnt */
 
@@ -2060,7 +2143,8 @@ static int xmit_skb(struct virtnet_sq *sq, struct sk_buff *skb)
 			return num_sg;
 		num_sg++;
 	}
-	return virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, skb, GFP_ATOMIC);
+
+	return virtnet_add_outbuf(sq, num_sg, skb);
 }
 
 static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
@@ -3717,6 +3801,8 @@ static void virtnet_free_queues(struct virtnet_info *vi)
 	for (i = 0; i < vi->max_queue_pairs; i++) {
 		__netif_napi_del(&vi->rq[i].napi);
 		__netif_napi_del(&vi->sq[i].napi);
+
+		kfree(vi->sq[i].dmainfo.head);
 	}
 
 	/* We called __netif_napi_del(),
@@ -3974,7 +4060,7 @@ static int init_vqs(struct virtnet_info *vi)
 	if (ret)
 		goto err_free;
 
-	virtnet_rq_set_premapped(vi);
+	virtnet_set_premapped(vi);
 
 	cpus_read_lock();
 	virtnet_set_affinity(vi);
diff --git a/drivers/net/virtio/virtio_net.h b/drivers/net/virtio/virtio_net.h
index 2f930af35364..cc742756e19a 100644
--- a/drivers/net/virtio/virtio_net.h
+++ b/drivers/net/virtio/virtio_net.h
@@ -7,6 +7,7 @@
 #include <linux/average.h>
 
 #define VIRTIO_XDP_FLAG	BIT(0)
+#define VIRTIO_XMIT_DATA_MASK (VIRTIO_XDP_FLAG)
 
 /* RX packet size EWMA. The average packet size is used to determine the packet
  * buffer size when refilling RX rings. As the entire RX ring may be refilled
@@ -58,6 +59,18 @@ struct virtnet_rq_dma {
 	u16 need_sync;
 };
 
+struct virtnet_sq_dma {
+	struct virtnet_sq_dma *next;
+	dma_addr_t addr;
+	u32 len;
+	void *data;
+};
+
+struct virtnet_sq_dma_head {
+	struct virtnet_sq_dma *free;
+	struct virtnet_sq_dma *head;
+};
+
 /* Internal representation of a send virtqueue */
 struct virtnet_sq {
 	/* Virtqueue associated with this virtnet_sq */
@@ -77,6 +90,10 @@ struct virtnet_sq {
 
 	/* Record whether sq is in reset state. */
 	bool reset;
+
+	bool do_dma;
+
+	struct virtnet_sq_dma_head dmainfo;
 };
 
 /* Internal representation of a receive virtqueue */
@@ -211,6 +228,29 @@ static inline struct xdp_frame *virtnet_ptr_to_xdp(void *ptr)
 	return (struct xdp_frame *)((unsigned long)ptr & ~VIRTIO_XDP_FLAG);
 }
 
+static inline void *virtnet_sq_unmap(struct virtnet_sq *sq, void *data)
+{
+	struct virtnet_sq_dma *next, *head;
+
+	head = (void *)((unsigned long)data & ~VIRTIO_XMIT_DATA_MASK);
+
+	data = head->data;
+
+	while (head) {
+		virtqueue_dma_unmap_single_attrs(sq->vq, head->addr, head->len,
+						 DMA_TO_DEVICE, 0);
+
+		next = head->next;
+
+		head->next = sq->dmainfo.free;
+		sq->dmainfo.free = head;
+
+		head = next;
+	}
+
+	return data;
+}
+
 static inline void virtnet_free_old_xmit(struct virtnet_sq *sq, bool in_napi,
 					 struct virtnet_sq_stats *stats)
 {
@@ -219,14 +259,24 @@ static inline void virtnet_free_old_xmit(struct virtnet_sq *sq, bool in_napi,
 
 	while ((ptr = virtqueue_get_buf(sq->vq, &len)) != NULL) {
 		if (!virtnet_is_xdp_frame(ptr)) {
-			struct sk_buff *skb = ptr;
+			struct sk_buff *skb;
+
+			if (sq->do_dma)
+				ptr = virtnet_sq_unmap(sq, ptr);
+
+			skb = ptr;
 
 			pr_debug("Sent skb %p\n", skb);
 
 			stats->bytes += skb->len;
 			napi_consume_skb(skb, in_napi);
 		} else {
-			struct xdp_frame *frame = virtnet_ptr_to_xdp(ptr);
+			struct xdp_frame *frame;
+
+			if (sq->do_dma)
+				ptr = virtnet_sq_unmap(sq, ptr);
+
+			frame = virtnet_ptr_to_xdp(ptr);
 
 			stats->bytes += xdp_get_frame_len(frame);
 			xdp_return_frame(frame);
-- 
2.32.0.3.g01195cf9f