Use page_pool for RX buffer allocation in mergeable and small buffer
modes to enable page recycling and avoid repeated page allocator calls.
skb_mark_for_recycle() enables page reuse in the network stack.

Big packets mode is unchanged because it uses page->private for linked
list chaining of multiple pages per buffer, which conflicts with
page_pool's internal use of page->private.

Implement conditional DMA premapping using virtqueue_dma_dev():
- When non-NULL (vhost, virtio-pci): use PP_FLAG_DMA_MAP with page_pool
  handling DMA mapping, submit via virtqueue_add_inbuf_premapped()
- When NULL (VDUSE, direct physical): page_pool handles allocation only,
  submit via virtqueue_add_inbuf_ctx()

This preserves the DMA premapping optimization from commit 31f3cd4e5756b
("virtio-net: rq submits premapped per-buffer") while adding page_pool
support as a prerequisite for future zero-copy features (devmem TCP,
io_uring ZCRX).

Page pools are created in probe and destroyed in remove (not open/close),
following existing driver behavior where RX buffers remain in virtqueues
across interface state changes.

The rx_mode_work_enabled flag prevents virtnet_rx_mode_work() from
sending control virtqueue commands while ndo_close is tearing down
device state, avoiding virtqueue corruption during concurrent operations.

Signed-off-by: Vishwanath Seshagiri <redacted>
---
 drivers/net/Kconfig      |   1 +
 drivers/net/virtio_net.c | 353 ++++++++++++++++++++++-----------------
 2 files changed, 203 insertions(+), 151 deletions(-)

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index ac12eaf11755..f1e6b6b0a86f 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig

@@ -450,6 +450,7 @@ config VIRTIO_NET
 	depends on VIRTIO
 	select NET_FAILOVER
 	select DIMLIB
+	select PAGE_POOL
 	help
 	  This is the virtual network driver for virtio.  It can be used with
 	  QEMU based VMMs (like KVM or Xen).  Say Y or M.

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index db88dcaefb20..df2a5fc5187e 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c

@@ -26,6 +26,7 @@
 #include <net/netdev_rx_queue.h>
 #include <net/netdev_queues.h>
 #include <net/xdp_sock_drv.h>
+#include <net/page_pool/helpers.h>
 
 static int napi_weight = NAPI_POLL_WEIGHT;
 module_param(napi_weight, int, 0444);

@@ -359,6 +360,11 @@ struct receive_queue {
 	/* Page frag for packet buffer allocation. */
 	struct page_frag alloc_frag;
 
+	struct page_pool *page_pool;
+
+	/* True if page_pool handles DMA mapping via PP_FLAG_DMA_MAP */
+	bool use_page_pool_dma;
+
 	/* RX: fragments + linear part + virtio header */
 	struct scatterlist sg[MAX_SKB_FRAGS + 2];
 

@@ -521,11 +527,13 @@ static int virtnet_xdp_handler(struct bpf_prog *xdp_prog, struct xdp_buff *xdp,
 			       struct virtnet_rq_stats *stats);
 static void virtnet_receive_done(struct virtnet_info *vi, struct receive_queue *rq,
 				 struct sk_buff *skb, u8 flags);
-static struct sk_buff *virtnet_skb_append_frag(struct sk_buff *head_skb,
+static struct sk_buff *virtnet_skb_append_frag(struct receive_queue *rq,
+					       struct sk_buff *head_skb,
 					       struct sk_buff *curr_skb,
 					       struct page *page, void *buf,
 					       int len, int truesize);
 static void virtnet_xsk_completed(struct send_queue *sq, int num);
+static void free_unused_bufs(struct virtnet_info *vi);
 
 enum virtnet_xmit_type {
 	VIRTNET_XMIT_TYPE_SKB,

@@ -706,15 +714,21 @@ static struct page *get_a_page(struct receive_queue *rq, gfp_t gfp_mask)
 	return p;
 }
 
+static void virtnet_put_page(struct receive_queue *rq, struct page *page,
+			     bool allow_direct)
+{
+	page_pool_put_page(rq->page_pool, page, -1, allow_direct);
+}
+
 static void virtnet_rq_free_buf(struct virtnet_info *vi,
 				struct receive_queue *rq, void *buf)
 {
 	if (vi->mergeable_rx_bufs)
-		put_page(virt_to_head_page(buf));
+		virtnet_put_page(rq, virt_to_head_page(buf), false);
 	else if (vi->big_packets)
 		give_pages(rq, buf);
 	else
-		put_page(virt_to_head_page(buf));
+		virtnet_put_page(rq, virt_to_head_page(buf), false);
 }

 
 static void enable_rx_mode_work(struct virtnet_info *vi)

@@ -877,9 +891,6 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
 		if (unlikely(!skb))
 			return NULL;
 
-		page = (struct page *)page->private;
-		if (page)
-			give_pages(rq, page);
 		goto ok;
 	}