[PATCH net-next v3 0/2] virtio_net: add page_pool support

[PATCH net-next v3 0/2] virtio_net: add page_pool support

[Vishwanath Seshagiri]

Introduce page_pool support in virtio_net driver to enable page
recycling in RX buffer allocation and avoid repeated page allocator
calls. This applies to mergeable and small buffer modes.

Beyond performance improvements, this patch is a prerequisite for
enabling memory provider-based zero-copy features in virtio_net, 
specifically devmem TCP and io_uring ZCRX, which require drivers to 
use page_pool for buffer management.

The implementation preserves the DMA premapping optimization introduced 
in commit 31f3cd4e5756 ("virtio-net: rq submits premapped per-buffer")
by conditionally using PP_FLAG_DMA_MAP when the virtio backend supports 
standard DMA API (vhost, virtio-pci), and falling back to
allocation-only mode for backends with custom DMA mechanisms (VDUSE).

================================================================================
                      VIRTIO-NET PAGE POOL BENCHMARK RESULTS
================================================================================

CONFIGURATION
-------------
- Host: pktgen TX → tap interface → vhost-net
- Guest: virtio-net RX → XDP_DROP
- Packet sizes: small buffers - 64; merge receivable 64, 1500

SMALL PACKETS (64 bytes) 
==================================================
Queues | Base (pps)  | Page Pool (pps) | Improvement | Base (Gb/s) |PP (Gb/s)
-------|-------------|-----------------|-------------|-------------|----------
  1Q   |    853,493  |      868,923    |   +1.8%     |    0.44     | 0.44
  2Q   |  1,655,793  |    1,696,707    |   +2.5%     |    0.85     | 0.87
  4Q   |  3,143,375  |    3,302,511    |   +5.1%     |    1.61     | 1.69
  8Q   |  6,082,590  |    6,156,894    |   +1.2%     |    3.11     | 3.15


RECEIVE MERGEABLE (64 bytes) 
======================================================
Queues | Base (pps)  | Page Pool (pps) | Improvement | Base (Gb/s) |PP (Gb/s)
-------|-------------|-----------------|-------------|-------------|----------
   1Q  |    766,168  |      814,493    |   +6.3%     |    0.39     | 0.42
   2Q  |  1,384,871  |    1,670,639    |  +20.6%     |    0.71     | 0.86
   4Q  |  2,773,081  |    3,080,574    |  +11.1%     |    1.42     | 1.58
   8Q  |  5,600,615  |    6,043,891    |   +7.9%     |    2.87     | 3.10


RECEIVE MERGEABLE (1500 bytes) 
========================================================
Queues | Base (pps)  | Page Pool (pps) | Improvement | Base (Gb/s) |PP (Gb/s)
-------|-------------|-----------------|-------------|-------------|----------
  1Q   |    741,579  |      785,442    |   +5.9%     |    8.90     | 9.43
  2Q   |  1,310,043  |    1,534,554    |  +17.1%     |   15.72     | 18.41
  4Q   |  2,748,700  |    2,890,582    |   +5.2%     |   32.98     | 34.69
  8Q   |  5,348,589  |    5,618,664    |   +5.0%     |   64.18     | 67.42

The page_pool implementation showed consistent performance improvements
by eliminating per packet overhead of allocating and deallocating
memory. When running the performance benchmarks, I noticed that
page_pool also had a consistent throughput performance compared to the
base patch where performance variability was due to accessing free_list
for getting the next set of pages.


Changes in v3
=============

Addressing reviewer feedback from v2:

- Fix CI null-ptr-deref crash: use max_queue_pairs instead of 
curr_queue_pairs in virtnet_create_page_pools() to ensure page pools 
are created for all queues (Jason Wang, Jakub Kicinski)
- Preserve big_packets mode page->private chaining in page_to_skb() with 
conditional checks (Jason Wang)
- Use page_pool_alloc_pages() in xdp_linearize_page() and 
mergeable_xdp_get_buf() to eliminate xdp_page tracking logic and simplify 
skb_mark_for_recycle() calls (Jason Wang)
- Add page_pool_page_is_pp() check in virtnet_put_page() to safely
  handle both page_pool and non-page_pool pages (Michael S. Tsirkin)
- Remove unrelated rx_mode_work_enabled changes (Jason Wang)
- Selftest: use random ephemeral port instead of hardcoded port to avoid conflicts 
when running tests in parallel (Michael S. Tsirkin)
- v2 link: https://lore.kernel.org/virtualization/20260128212031.1431746-1-vishs@meta.com/ 

Changes in v2
=============

Addressing reviewer feedback from v1:

- Add "select PAGE_POOL" to Kconfig (Jason Wang)
- Move page pool creation from ndo_open to probe for device lifetime
  management (Xuan Zhuo, Jason Wang)
- Implement conditional DMA strategy using virtqueue_dma_dev():
  - When non-NULL: use PP_FLAG_DMA_MAP for page_pool-managed DMA
    premapping
  - When NULL (VDUSE): page_pool handles allocation only
- Use page_pool_get_dma_addr() + virtqueue_add_inbuf_premapped() to
  preserve DMA premapping optimization from commit 31f3cd4e5756
  ("virtio-net: rq submits premapped per-buffer") (Jason Wang)
- Remove dual allocation code paths - page_pool now always used for
  small/mergeable modes (Jason Wang)
- Remove unused virtnet_rq_alloc/virtnet_rq_init_one_sg functions
- Add comprehensive performance data (Michael S. Tsirkin)
- v1 link:
  https://lore.kernel.org/virtualization/20260106221924.123856-1-vishs@meta.com/


Vishwanath Seshagiri (2):
  virtio_net: add page_pool support for buffer allocation
  selftests: virtio_net: add buffer circulation test

 drivers/net/Kconfig                           |   1 +
 drivers/net/virtio_net.c                      | 360 ++++++++++--------
 .../drivers/net/virtio_net/basic_features.sh  |  86 +++++
 3 files changed, 292 insertions(+), 155 deletions(-)

-- 
2.47.3

[PATCH net-next v3 1/2] virtio_net: add page_pool support for buffer allocation

[Vishwanath Seshagiri]

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.

Signed-off-by: Vishwanath Seshagiri <vishs@meta.com>
---
 drivers/net/Kconfig      |   1 +
 drivers/net/virtio_net.c | 360 ++++++++++++++++++++++-----------------
 2 files changed, 206 insertions(+), 155 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..52632361c1f8 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 +714,24 @@ 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)
+{
+	if (page_pool_page_is_pp(page))
+		page_pool_put_page(rq->page_pool, page, -1, allow_direct);
+	else
+		put_page(page);
+}
+
 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 +894,12 @@ 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);
+		if (!rq->page_pool) {
+			page = (struct page *)page->private;
+			if (page)
+				give_pages(rq, page);
+		}
+
 		goto ok;
 	}
 
@@ -914,7 +934,10 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
 		skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page, offset,
 				frag_size, truesize);
 		len -= frag_size;
-		page = (struct page *)page->private;
+		if (!rq->page_pool)
+			page = (struct page *)page->private;
+		else
+			page = NULL;
 		offset = 0;
 	}
 
@@ -925,7 +948,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
 	hdr = skb_vnet_common_hdr(skb);
 	memcpy(hdr, hdr_p, hdr_len);
 	if (page_to_free)
-		put_page(page_to_free);
+		virtnet_put_page(rq, page_to_free, true);
 
 	return skb;
 }
@@ -965,93 +988,10 @@ static void virtnet_rq_unmap(struct receive_queue *rq, void *buf, u32 len)
 static void *virtnet_rq_get_buf(struct receive_queue *rq, u32 *len, void **ctx)
 {
 	struct virtnet_info *vi = rq->vq->vdev->priv;
-	void *buf;
-
-	BUG_ON(vi->big_packets && !vi->mergeable_rx_bufs);
-
-	buf = virtqueue_get_buf_ctx(rq->vq, len, ctx);
-	if (buf)
-		virtnet_rq_unmap(rq, buf, *len);
-
-	return buf;
-}
-
-static void virtnet_rq_init_one_sg(struct receive_queue *rq, void *buf, u32 len)
-{
-	struct virtnet_info *vi = rq->vq->vdev->priv;
-	struct virtnet_rq_dma *dma;
-	dma_addr_t addr;
-	u32 offset;
-	void *head;
-
-	BUG_ON(vi->big_packets && !vi->mergeable_rx_bufs);
-
-	head = page_address(rq->alloc_frag.page);
-
-	offset = buf - head;
-
-	dma = head;
-
-	addr = dma->addr - sizeof(*dma) + offset;
-
-	sg_init_table(rq->sg, 1);
-	sg_fill_dma(rq->sg, addr, len);
-}
-
-static void *virtnet_rq_alloc(struct receive_queue *rq, u32 size, gfp_t gfp)
-{
-	struct page_frag *alloc_frag = &rq->alloc_frag;
-	struct virtnet_info *vi = rq->vq->vdev->priv;
-	struct virtnet_rq_dma *dma;
-	void *buf, *head;
-	dma_addr_t addr;
 
 	BUG_ON(vi->big_packets && !vi->mergeable_rx_bufs);
 
-	head = page_address(alloc_frag->page);
-
-	dma = head;
-
-	/* new pages */
-	if (!alloc_frag->offset) {
-		if (rq->last_dma) {
-			/* Now, the new page is allocated, the last dma
-			 * will not be used. So the dma can be unmapped
-			 * if the ref is 0.
-			 */
-			virtnet_rq_unmap(rq, rq->last_dma, 0);
-			rq->last_dma = NULL;
-		}
-
-		dma->len = alloc_frag->size - sizeof(*dma);
-
-		addr = virtqueue_map_single_attrs(rq->vq, dma + 1,
-						  dma->len, DMA_FROM_DEVICE, 0);
-		if (virtqueue_map_mapping_error(rq->vq, addr))
-			return NULL;
-
-		dma->addr = addr;
-		dma->need_sync = virtqueue_map_need_sync(rq->vq, addr);
-
-		/* Add a reference to dma to prevent the entire dma from
-		 * being released during error handling. This reference
-		 * will be freed after the pages are no longer used.
-		 */
-		get_page(alloc_frag->page);
-		dma->ref = 1;
-		alloc_frag->offset = sizeof(*dma);
-
-		rq->last_dma = dma;
-	}
-
-	++dma->ref;
-
-	buf = head + alloc_frag->offset;
-
-	get_page(alloc_frag->page);
-	alloc_frag->offset += size;
-
-	return buf;
+	return virtqueue_get_buf_ctx(rq->vq, len, ctx);
 }
 
 static void virtnet_rq_unmap_free_buf(struct virtqueue *vq, void *buf)
@@ -1067,9 +1007,6 @@ static void virtnet_rq_unmap_free_buf(struct virtqueue *vq, void *buf)
 		return;
 	}
 
-	if (!vi->big_packets || vi->mergeable_rx_bufs)
-		virtnet_rq_unmap(rq, buf, 0);
-
 	virtnet_rq_free_buf(vi, rq, buf);
 }
 
@@ -1335,7 +1272,7 @@ static int xsk_append_merge_buffer(struct virtnet_info *vi,
 
 		truesize = len;
 
-		curr_skb  = virtnet_skb_append_frag(head_skb, curr_skb, page,
+		curr_skb  = virtnet_skb_append_frag(rq, head_skb, curr_skb, page,
 						    buf, len, truesize);
 		if (!curr_skb) {
 			put_page(page);
@@ -1771,7 +1708,7 @@ static int virtnet_xdp_xmit(struct net_device *dev,
 	return ret;
 }
 
-static void put_xdp_frags(struct xdp_buff *xdp)
+static void put_xdp_frags(struct xdp_buff *xdp, struct receive_queue *rq)
 {
 	struct skb_shared_info *shinfo;
 	struct page *xdp_page;
@@ -1781,7 +1718,7 @@ static void put_xdp_frags(struct xdp_buff *xdp)
 		shinfo = xdp_get_shared_info_from_buff(xdp);
 		for (i = 0; i < shinfo->nr_frags; i++) {
 			xdp_page = skb_frag_page(&shinfo->frags[i]);
-			put_page(xdp_page);
+			virtnet_put_page(rq, xdp_page, true);
 		}
 	}
 }
@@ -1873,7 +1810,7 @@ static struct page *xdp_linearize_page(struct net_device *dev,
 	if (page_off + *len + tailroom > PAGE_SIZE)
 		return NULL;
 
-	page = alloc_page(GFP_ATOMIC);
+	page = page_pool_alloc_pages(rq->page_pool, GFP_ATOMIC);
 	if (!page)
 		return NULL;
 
@@ -1897,7 +1834,7 @@ static struct page *xdp_linearize_page(struct net_device *dev,
 		off = buf - page_address(p);
 
 		if (check_mergeable_len(dev, ctx, buflen)) {
-			put_page(p);
+			virtnet_put_page(rq, p, true);
 			goto err_buf;
 		}
 
@@ -1905,21 +1842,21 @@ static struct page *xdp_linearize_page(struct net_device *dev,
 		 * is sending packet larger than the MTU.
 		 */
 		if ((page_off + buflen + tailroom) > PAGE_SIZE) {
-			put_page(p);
+			virtnet_put_page(rq, p, true);
 			goto err_buf;
 		}
 
 		memcpy(page_address(page) + page_off,
 		       page_address(p) + off, buflen);
 		page_off += buflen;
-		put_page(p);
+		virtnet_put_page(rq, p, true);
 	}
 
 	/* Headroom does not contribute to packet length */
 	*len = page_off - XDP_PACKET_HEADROOM;
 	return page;
 err_buf:
-	__free_pages(page, 0);
+	page_pool_put_page(rq->page_pool, page, -1, true);
 	return NULL;
 }
 
@@ -1962,7 +1899,7 @@ static struct sk_buff *receive_small_xdp(struct net_device *dev,
 	unsigned int headroom = vi->hdr_len + header_offset;
 	struct virtio_net_hdr_mrg_rxbuf *hdr = buf + header_offset;
 	struct page *page = virt_to_head_page(buf);
-	struct page *xdp_page;
+	struct page *xdp_page = NULL;
 	unsigned int buflen;
 	struct xdp_buff xdp;
 	struct sk_buff *skb;
@@ -1996,7 +1933,7 @@ static struct sk_buff *receive_small_xdp(struct net_device *dev,
 			goto err_xdp;
 
 		buf = page_address(xdp_page);
-		put_page(page);
+		virtnet_put_page(rq, page, true);
 		page = xdp_page;
 	}
 
@@ -2028,13 +1965,15 @@ static struct sk_buff *receive_small_xdp(struct net_device *dev,
 	if (metasize)
 		skb_metadata_set(skb, metasize);
 
+	skb_mark_for_recycle(skb);
+
 	return skb;
 
 err_xdp:
 	u64_stats_inc(&stats->xdp_drops);
 err:
 	u64_stats_inc(&stats->drops);
-	put_page(page);
+	virtnet_put_page(rq, page, true);
 xdp_xmit:
 	return NULL;
 }
@@ -2082,12 +2021,14 @@ static struct sk_buff *receive_small(struct net_device *dev,
 	}
 
 	skb = receive_small_build_skb(vi, xdp_headroom, buf, len);
-	if (likely(skb))
+	if (likely(skb)) {
+		skb_mark_for_recycle(skb);
 		return skb;
+	}
 
 err:
 	u64_stats_inc(&stats->drops);
-	put_page(page);
+	virtnet_put_page(rq, page, true);
 	return NULL;
 }
 
@@ -2142,7 +2083,7 @@ static void mergeable_buf_free(struct receive_queue *rq, int num_buf,
 		}
 		u64_stats_add(&stats->bytes, len);
 		page = virt_to_head_page(buf);
-		put_page(page);
+		virtnet_put_page(rq, page, true);
 	}
 }
 
@@ -2253,7 +2194,7 @@ static int virtnet_build_xdp_buff_mrg(struct net_device *dev,
 		offset = buf - page_address(page);
 
 		if (check_mergeable_len(dev, ctx, len)) {
-			put_page(page);
+			virtnet_put_page(rq, page, true);
 			goto err;
 		}
 
@@ -2272,7 +2213,7 @@ static int virtnet_build_xdp_buff_mrg(struct net_device *dev,
 	return 0;
 
 err:
-	put_xdp_frags(xdp);
+	put_xdp_frags(xdp, rq);
 	return -EINVAL;
 }
 
@@ -2337,7 +2278,7 @@ static void *mergeable_xdp_get_buf(struct virtnet_info *vi,
 		if (*len + xdp_room > PAGE_SIZE)
 			return NULL;
 
-		xdp_page = alloc_page(GFP_ATOMIC);
+		xdp_page = page_pool_alloc_pages(rq->page_pool, GFP_ATOMIC);
 		if (!xdp_page)
 			return NULL;
 
@@ -2347,7 +2288,7 @@ static void *mergeable_xdp_get_buf(struct virtnet_info *vi,
 
 	*frame_sz = PAGE_SIZE;
 
-	put_page(*page);
+	virtnet_put_page(rq, *page, true);
 
 	*page = xdp_page;
 
@@ -2393,6 +2334,8 @@ static struct sk_buff *receive_mergeable_xdp(struct net_device *dev,
 		head_skb = build_skb_from_xdp_buff(dev, vi, &xdp, xdp_frags_truesz);
 		if (unlikely(!head_skb))
 			break;
+
+		skb_mark_for_recycle(head_skb);
 		return head_skb;
 
 	case XDP_TX:
@@ -2403,10 +2346,10 @@ static struct sk_buff *receive_mergeable_xdp(struct net_device *dev,
 		break;
 	}
 
-	put_xdp_frags(&xdp);
+	put_xdp_frags(&xdp, rq);
 
 err_xdp:
-	put_page(page);
+	virtnet_put_page(rq, page, true);
 	mergeable_buf_free(rq, num_buf, dev, stats);
 
 	u64_stats_inc(&stats->xdp_drops);
@@ -2414,7 +2357,8 @@ static struct sk_buff *receive_mergeable_xdp(struct net_device *dev,
 	return NULL;
 }
 
-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)
@@ -2446,7 +2390,7 @@ static struct sk_buff *virtnet_skb_append_frag(struct sk_buff *head_skb,
 
 	offset = buf - page_address(page);
 	if (skb_can_coalesce(curr_skb, num_skb_frags, page, offset)) {
-		put_page(page);
+		virtnet_put_page(rq, page, true);
 		skb_coalesce_rx_frag(curr_skb, num_skb_frags - 1,
 				     len, truesize);
 	} else {
@@ -2499,6 +2443,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 
 	if (unlikely(!curr_skb))
 		goto err_skb;
+
+	skb_mark_for_recycle(head_skb);
 	while (--num_buf) {
 		buf = virtnet_rq_get_buf(rq, &len, &ctx);
 		if (unlikely(!buf)) {
@@ -2517,7 +2463,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 			goto err_skb;
 
 		truesize = mergeable_ctx_to_truesize(ctx);
-		curr_skb  = virtnet_skb_append_frag(head_skb, curr_skb, page,
+		curr_skb  = virtnet_skb_append_frag(rq, head_skb, curr_skb, page,
 						    buf, len, truesize);
 		if (!curr_skb)
 			goto err_skb;
@@ -2527,7 +2473,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 	return head_skb;
 
 err_skb:
-	put_page(page);
+	virtnet_put_page(rq, page, true);
 	mergeable_buf_free(rq, num_buf, dev, stats);
 
 err_buf:
@@ -2666,32 +2612,42 @@ static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
 static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
 			     gfp_t gfp)
 {
-	char *buf;
 	unsigned int xdp_headroom = virtnet_get_headroom(vi);
 	void *ctx = (void *)(unsigned long)xdp_headroom;
 	int len = vi->hdr_len + VIRTNET_RX_PAD + GOOD_PACKET_LEN + xdp_headroom;
+	unsigned int offset;
+	struct page *page;
+	dma_addr_t addr;
+	char *buf;
 	int err;
 
 	len = SKB_DATA_ALIGN(len) +
 	      SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
 
-	if (unlikely(!skb_page_frag_refill(len, &rq->alloc_frag, gfp)))
-		return -ENOMEM;
-
-	buf = virtnet_rq_alloc(rq, len, gfp);
-	if (unlikely(!buf))
+	page = page_pool_alloc_frag(rq->page_pool, &offset, len, gfp);
+	if (unlikely(!page))
 		return -ENOMEM;
 
+	buf = page_address(page) + offset;
 	buf += VIRTNET_RX_PAD + xdp_headroom;
 
-	virtnet_rq_init_one_sg(rq, buf, vi->hdr_len + GOOD_PACKET_LEN);
+	if (rq->use_page_pool_dma) {
+		addr = page_pool_get_dma_addr(page) + offset;
+		addr += VIRTNET_RX_PAD + xdp_headroom;
 
-	err = virtqueue_add_inbuf_premapped(rq->vq, rq->sg, 1, buf, ctx, gfp);
-	if (err < 0) {
-		virtnet_rq_unmap(rq, buf, 0);
-		put_page(virt_to_head_page(buf));
+		sg_init_table(rq->sg, 1);
+		sg_fill_dma(rq->sg, addr, vi->hdr_len + GOOD_PACKET_LEN);
+		err = virtqueue_add_inbuf_premapped(rq->vq, rq->sg, 1,
+						    buf, ctx, gfp);
+	} else {
+		sg_init_one(rq->sg, buf, vi->hdr_len + GOOD_PACKET_LEN);
+		err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1,
+					      buf, ctx, gfp);
 	}
 
+	if (err < 0)
+		page_pool_put_page(rq->page_pool, virt_to_head_page(buf),
+				   -1, false);
 	return err;
 }
 
@@ -2764,13 +2720,15 @@ static unsigned int get_mergeable_buf_len(struct receive_queue *rq,
 static int add_recvbuf_mergeable(struct virtnet_info *vi,
 				 struct receive_queue *rq, gfp_t gfp)
 {
-	struct page_frag *alloc_frag = &rq->alloc_frag;
 	unsigned int headroom = virtnet_get_headroom(vi);
 	unsigned int tailroom = headroom ? sizeof(struct skb_shared_info) : 0;
 	unsigned int room = SKB_DATA_ALIGN(headroom + tailroom);
 	unsigned int len, hole;
-	void *ctx;
+	unsigned int offset;
+	struct page *page;
+	dma_addr_t addr;
 	char *buf;
+	void *ctx;
 	int err;
 
 	/* Extra tailroom is needed to satisfy XDP's assumption. This
@@ -2779,18 +2737,14 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
 	 */
 	len = get_mergeable_buf_len(rq, &rq->mrg_avg_pkt_len, room);
 
-	if (unlikely(!skb_page_frag_refill(len + room, alloc_frag, gfp)))
-		return -ENOMEM;
-
-	if (!alloc_frag->offset && len + room + sizeof(struct virtnet_rq_dma) > alloc_frag->size)
-		len -= sizeof(struct virtnet_rq_dma);
-
-	buf = virtnet_rq_alloc(rq, len + room, gfp);
-	if (unlikely(!buf))
+	page = page_pool_alloc_frag(rq->page_pool, &offset, len + room, gfp);
+	if (unlikely(!page))
 		return -ENOMEM;
 
+	buf = page_address(page) + offset;
 	buf += headroom; /* advance address leaving hole at front of pkt */
-	hole = alloc_frag->size - alloc_frag->offset;
+
+	hole = PAGE_SIZE - (offset + len + room);
 	if (hole < len + room) {
 		/* To avoid internal fragmentation, if there is very likely not
 		 * enough space for another buffer, add the remaining space to
@@ -2800,18 +2754,27 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
 		 */
 		if (!headroom)
 			len += hole;
-		alloc_frag->offset += hole;
 	}
 
-	virtnet_rq_init_one_sg(rq, buf, len);
-
 	ctx = mergeable_len_to_ctx(len + room, headroom);
-	err = virtqueue_add_inbuf_premapped(rq->vq, rq->sg, 1, buf, ctx, gfp);
-	if (err < 0) {
-		virtnet_rq_unmap(rq, buf, 0);
-		put_page(virt_to_head_page(buf));
+
+	if (rq->use_page_pool_dma) {
+		addr = page_pool_get_dma_addr(page) + offset;
+		addr += headroom;
+
+		sg_init_table(rq->sg, 1);
+		sg_fill_dma(rq->sg, addr, len);
+		err = virtqueue_add_inbuf_premapped(rq->vq, rq->sg, 1,
+						    buf, ctx, gfp);
+	} else {
+		sg_init_one(rq->sg, buf, len);
+		err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1,
+					      buf, ctx, gfp);
 	}
 
+	if (err < 0)
+		page_pool_put_page(rq->page_pool, virt_to_head_page(buf),
+				   -1, false);
 	return err;
 }
 
@@ -3128,7 +3091,10 @@ static int virtnet_enable_queue_pair(struct virtnet_info *vi, int qp_index)
 		return err;
 
 	err = xdp_rxq_info_reg_mem_model(&vi->rq[qp_index].xdp_rxq,
-					 MEM_TYPE_PAGE_SHARED, NULL);
+					 vi->rq[qp_index].page_pool ?
+						MEM_TYPE_PAGE_POOL :
+						MEM_TYPE_PAGE_SHARED,
+					 vi->rq[qp_index].page_pool);
 	if (err < 0)
 		goto err_xdp_reg_mem_model;
 
@@ -3168,6 +3134,81 @@ static void virtnet_update_settings(struct virtnet_info *vi)
 		vi->duplex = duplex;
 }
 
+static int virtnet_create_page_pools(struct virtnet_info *vi)
+{
+	int i, err;
+
+	for (i = 0; i < vi->max_queue_pairs; i++) {
+		struct receive_queue *rq = &vi->rq[i];
+		struct page_pool_params pp_params = { 0 };
+		struct device *dma_dev;
+
+		if (rq->page_pool)
+			continue;
+
+		if (rq->xsk_pool)
+			continue;
+
+		if (!vi->mergeable_rx_bufs && vi->big_packets)
+			continue;
+
+		pp_params.order = 0;
+		pp_params.pool_size = virtqueue_get_vring_size(rq->vq);
+		pp_params.nid = dev_to_node(vi->vdev->dev.parent);
+		pp_params.netdev = vi->dev;
+		pp_params.napi = &rq->napi;
+
+		/* Check if backend supports DMA API (e.g., vhost, virtio-pci).
+		 * If so, use page_pool's DMA mapping for premapped buffers.
+		 * Otherwise (e.g., VDUSE), page_pool only handles allocation.
+		 */
+		dma_dev = virtqueue_dma_dev(rq->vq);
+		if (dma_dev) {
+			pp_params.dev = dma_dev;
+			pp_params.flags = PP_FLAG_DMA_MAP;
+			pp_params.dma_dir = DMA_FROM_DEVICE;
+			rq->use_page_pool_dma = true;
+		} else {
+			pp_params.dev = vi->vdev->dev.parent;
+			pp_params.flags = 0;
+			rq->use_page_pool_dma = false;
+		}
+
+		rq->page_pool = page_pool_create(&pp_params);
+		if (IS_ERR(rq->page_pool)) {
+			err = PTR_ERR(rq->page_pool);
+			rq->page_pool = NULL;
+			goto err_cleanup;
+		}
+	}
+	return 0;
+
+err_cleanup:
+	while (--i >= 0) {
+		struct receive_queue *rq = &vi->rq[i];
+
+		if (rq->page_pool) {
+			page_pool_destroy(rq->page_pool);
+			rq->page_pool = NULL;
+		}
+	}
+	return err;
+}
+
+static void virtnet_destroy_page_pools(struct virtnet_info *vi)
+{
+	int i;
+
+	for (i = 0; i < vi->max_queue_pairs; i++) {
+		struct receive_queue *rq = &vi->rq[i];
+
+		if (rq->page_pool) {
+			page_pool_destroy(rq->page_pool);
+			rq->page_pool = NULL;
+		}
+	}
+}
+
 static int virtnet_open(struct net_device *dev)
 {
 	struct virtnet_info *vi = netdev_priv(dev);
@@ -3770,7 +3811,6 @@ static int virtnet_close(struct net_device *dev)
 	 * open
 	 */
 	cancel_work_sync(&vi->config_work);
-
 	for (i = 0; i < vi->max_queue_pairs; i++) {
 		virtnet_disable_queue_pair(vi, i);
 		virtnet_cancel_dim(vi, &vi->rq[i].dim);
@@ -6442,9 +6482,6 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
 		vi->sq[i].vq = vqs[txq2vq(i)];
 	}
 
-	/* run here: ret == 0. */
-
-
 err_find:
 	kfree(ctx);
 err_ctx:
@@ -6945,6 +6982,14 @@ static int virtnet_probe(struct virtio_device *vdev)
 			goto free;
 	}
 
+	/* Create page pools for receive queues.
+	 * Page pools are created at probe time so they can be used
+	 * with premapped DMA addresses throughout the device lifetime.
+	 */
+	err = virtnet_create_page_pools(vi);
+	if (err)
+		goto free_irq_moder;
+
 #ifdef CONFIG_SYSFS
 	if (vi->mergeable_rx_bufs)
 		dev->sysfs_rx_queue_group = &virtio_net_mrg_rx_group;
@@ -6958,7 +7003,7 @@ static int virtnet_probe(struct virtio_device *vdev)
 		vi->failover = net_failover_create(vi->dev);
 		if (IS_ERR(vi->failover)) {
 			err = PTR_ERR(vi->failover);
-			goto free_vqs;
+			goto free_page_pools;
 		}
 	}
 
@@ -7075,7 +7120,10 @@ static int virtnet_probe(struct virtio_device *vdev)
 	unregister_netdev(dev);
 free_failover:
 	net_failover_destroy(vi->failover);
-free_vqs:
+free_page_pools:
+	virtnet_destroy_page_pools(vi);
+free_irq_moder:
+	virtnet_free_irq_moder(vi);
 	virtio_reset_device(vdev);
 	free_receive_page_frags(vi);
 	virtnet_del_vqs(vi);
@@ -7104,6 +7152,8 @@ static void remove_vq_common(struct virtnet_info *vi)
 
 	free_receive_page_frags(vi);
 
+	virtnet_destroy_page_pools(vi);
+
 	virtnet_del_vqs(vi);
 }
 
-- 
2.47.3

Re: [PATCH net-next v3 1/2] virtio_net: add page_pool support for buffer allocation

[Jason Wang]

On Wed, Feb 4, 2026 at 7:10 AM Vishwanath Seshagiri <vishs@meta.com> wrote:
>
> 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.
>
> Signed-off-by: Vishwanath Seshagiri <vishs@meta.com>
> ---
>  drivers/net/Kconfig      |   1 +
>  drivers/net/virtio_net.c | 360 ++++++++++++++++++++++-----------------
>  2 files changed, 206 insertions(+), 155 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..52632361c1f8 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 +714,24 @@ 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)
> +{
> +       if (page_pool_page_is_pp(page))
> +               page_pool_put_page(rq->page_pool, page, -1, allow_direct);
> +       else
> +               put_page(page);
> +}
> +
>  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 +894,12 @@ 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);
> +               if (!rq->page_pool) {
> +                       page = (struct page *)page->private;
> +                       if (page)
> +                               give_pages(rq, page);
> +               }
> +
>                 goto ok;
>         }
>
> @@ -914,7 +934,10 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
>                 skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page, offset,
>                                 frag_size, truesize);
>                 len -= frag_size;
> -               page = (struct page *)page->private;
> +               if (!rq->page_pool)
> +                       page = (struct page *)page->private;
> +               else
> +                       page = NULL;

The check seems to be unnecessary as page_to_skb() will be only called
by big and mergeable. And we goto ok for mergeable before.

>                 offset = 0;
>         }
>
> @@ -925,7 +948,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
>         hdr = skb_vnet_common_hdr(skb);
>         memcpy(hdr, hdr_p, hdr_len);
>         if (page_to_free)
> -               put_page(page_to_free);
> +               virtnet_put_page(rq, page_to_free, true);
>
>         return skb;
>  }
> @@ -965,93 +988,10 @@ static void virtnet_rq_unmap(struct receive_queue *rq, void *buf, u32 len)
>  static void *virtnet_rq_get_buf(struct receive_queue *rq, u32 *len, void **ctx)
>  {
>         struct virtnet_info *vi = rq->vq->vdev->priv;
> -       void *buf;
> -
> -       BUG_ON(vi->big_packets && !vi->mergeable_rx_bufs);
> -
> -       buf = virtqueue_get_buf_ctx(rq->vq, len, ctx);
> -       if (buf)
> -               virtnet_rq_unmap(rq, buf, *len);
> -
> -       return buf;
> -}
> -
> -static void virtnet_rq_init_one_sg(struct receive_queue *rq, void *buf, u32 len)
> -{
> -       struct virtnet_info *vi = rq->vq->vdev->priv;
> -       struct virtnet_rq_dma *dma;
> -       dma_addr_t addr;
> -       u32 offset;
> -       void *head;
> -
> -       BUG_ON(vi->big_packets && !vi->mergeable_rx_bufs);
> -
> -       head = page_address(rq->alloc_frag.page);
> -
> -       offset = buf - head;
> -
> -       dma = head;
> -
> -       addr = dma->addr - sizeof(*dma) + offset;
> -
> -       sg_init_table(rq->sg, 1);
> -       sg_fill_dma(rq->sg, addr, len);
> -}
> -
> -static void *virtnet_rq_alloc(struct receive_queue *rq, u32 size, gfp_t gfp)
> -{
> -       struct page_frag *alloc_frag = &rq->alloc_frag;
> -       struct virtnet_info *vi = rq->vq->vdev->priv;
> -       struct virtnet_rq_dma *dma;
> -       void *buf, *head;
> -       dma_addr_t addr;
>
>         BUG_ON(vi->big_packets && !vi->mergeable_rx_bufs);
>
> -       head = page_address(alloc_frag->page);
> -
> -       dma = head;
> -
> -       /* new pages */
> -       if (!alloc_frag->offset) {
> -               if (rq->last_dma) {
> -                       /* Now, the new page is allocated, the last dma
> -                        * will not be used. So the dma can be unmapped
> -                        * if the ref is 0.
> -                        */
> -                       virtnet_rq_unmap(rq, rq->last_dma, 0);
> -                       rq->last_dma = NULL;
> -               }
> -
> -               dma->len = alloc_frag->size - sizeof(*dma);
> -
> -               addr = virtqueue_map_single_attrs(rq->vq, dma + 1,
> -                                                 dma->len, DMA_FROM_DEVICE, 0);
> -               if (virtqueue_map_mapping_error(rq->vq, addr))
> -                       return NULL;
> -
> -               dma->addr = addr;
> -               dma->need_sync = virtqueue_map_need_sync(rq->vq, addr);
> -
> -               /* Add a reference to dma to prevent the entire dma from
> -                * being released during error handling. This reference
> -                * will be freed after the pages are no longer used.
> -                */
> -               get_page(alloc_frag->page);
> -               dma->ref = 1;
> -               alloc_frag->offset = sizeof(*dma);
> -
> -               rq->last_dma = dma;
> -       }
> -
> -       ++dma->ref;
> -
> -       buf = head + alloc_frag->offset;
> -
> -       get_page(alloc_frag->page);
> -       alloc_frag->offset += size;
> -
> -       return buf;
> +       return virtqueue_get_buf_ctx(rq->vq, len, ctx);
>  }
>
>  static void virtnet_rq_unmap_free_buf(struct virtqueue *vq, void *buf)
> @@ -1067,9 +1007,6 @@ static void virtnet_rq_unmap_free_buf(struct virtqueue *vq, void *buf)
>                 return;
>         }
>
> -       if (!vi->big_packets || vi->mergeable_rx_bufs)
> -               virtnet_rq_unmap(rq, buf, 0);
> -
>         virtnet_rq_free_buf(vi, rq, buf);
>  }
>
> @@ -1335,7 +1272,7 @@ static int xsk_append_merge_buffer(struct virtnet_info *vi,
>
>                 truesize = len;
>
> -               curr_skb  = virtnet_skb_append_frag(head_skb, curr_skb, page,
> +               curr_skb  = virtnet_skb_append_frag(rq, head_skb, curr_skb, page,
>                                                     buf, len, truesize);
>                 if (!curr_skb) {
>                         put_page(page);
> @@ -1771,7 +1708,7 @@ static int virtnet_xdp_xmit(struct net_device *dev,
>         return ret;
>  }
>
> -static void put_xdp_frags(struct xdp_buff *xdp)
> +static void put_xdp_frags(struct xdp_buff *xdp, struct receive_queue *rq)

Nit: rq may come first to align with append_frags()?

>  {
>         struct skb_shared_info *shinfo;
>         struct page *xdp_page;
> @@ -1781,7 +1718,7 @@ static void put_xdp_frags(struct xdp_buff *xdp)
>                 shinfo = xdp_get_shared_info_from_buff(xdp);
>                 for (i = 0; i < shinfo->nr_frags; i++) {
>                         xdp_page = skb_frag_page(&shinfo->frags[i]);
> -                       put_page(xdp_page);
> +                       virtnet_put_page(rq, xdp_page, true);
>                 }
>         }
>  }
> @@ -1873,7 +1810,7 @@ static struct page *xdp_linearize_page(struct net_device *dev,
>         if (page_off + *len + tailroom > PAGE_SIZE)
>                 return NULL;
>
> -       page = alloc_page(GFP_ATOMIC);
> +       page = page_pool_alloc_pages(rq->page_pool, GFP_ATOMIC);
>         if (!page)
>                 return NULL;
>
> @@ -1897,7 +1834,7 @@ static struct page *xdp_linearize_page(struct net_device *dev,
>                 off = buf - page_address(p);
>
>                 if (check_mergeable_len(dev, ctx, buflen)) {
> -                       put_page(p);
> +                       virtnet_put_page(rq, p, true);
>                         goto err_buf;
>                 }
>
> @@ -1905,21 +1842,21 @@ static struct page *xdp_linearize_page(struct net_device *dev,
>                  * is sending packet larger than the MTU.
>                  */
>                 if ((page_off + buflen + tailroom) > PAGE_SIZE) {
> -                       put_page(p);
> +                       virtnet_put_page(rq, p, true);
>                         goto err_buf;
>                 }
>
>                 memcpy(page_address(page) + page_off,
>                        page_address(p) + off, buflen);
>                 page_off += buflen;
> -               put_page(p);
> +               virtnet_put_page(rq, p, true);
>         }
>
>         /* Headroom does not contribute to packet length */
>         *len = page_off - XDP_PACKET_HEADROOM;
>         return page;
>  err_buf:
> -       __free_pages(page, 0);
> +       page_pool_put_page(rq->page_pool, page, -1, true);
>         return NULL;
>  }
>
> @@ -1962,7 +1899,7 @@ static struct sk_buff *receive_small_xdp(struct net_device *dev,
>         unsigned int headroom = vi->hdr_len + header_offset;
>         struct virtio_net_hdr_mrg_rxbuf *hdr = buf + header_offset;
>         struct page *page = virt_to_head_page(buf);
> -       struct page *xdp_page;
> +       struct page *xdp_page = NULL;

This seems unnecessary.

>         unsigned int buflen;
>         struct xdp_buff xdp;
>         struct sk_buff *skb;
> @@ -1996,7 +1933,7 @@ static struct sk_buff *receive_small_xdp(struct net_device *dev,
>                         goto err_xdp;
>
>                 buf = page_address(xdp_page);
> -               put_page(page);
> +               virtnet_put_page(rq, page, true);
>                 page = xdp_page;
>         }
>
> @@ -2028,13 +1965,15 @@ static struct sk_buff *receive_small_xdp(struct net_device *dev,
>         if (metasize)
>                 skb_metadata_set(skb, metasize);
>
> +       skb_mark_for_recycle(skb);
> +
>         return skb;
>
>  err_xdp:
>         u64_stats_inc(&stats->xdp_drops);
>  err:
>         u64_stats_inc(&stats->drops);
> -       put_page(page);
> +       virtnet_put_page(rq, page, true);
>  xdp_xmit:
>         return NULL;
>  }
> @@ -2082,12 +2021,14 @@ static struct sk_buff *receive_small(struct net_device *dev,
>         }
>
>         skb = receive_small_build_skb(vi, xdp_headroom, buf, len);
> -       if (likely(skb))
> +       if (likely(skb)) {
> +               skb_mark_for_recycle(skb);
>                 return skb;
> +       }
>
>  err:
>         u64_stats_inc(&stats->drops);
> -       put_page(page);
> +       virtnet_put_page(rq, page, true);
>         return NULL;
>  }
>
> @@ -2142,7 +2083,7 @@ static void mergeable_buf_free(struct receive_queue *rq, int num_buf,
>                 }
>                 u64_stats_add(&stats->bytes, len);
>                 page = virt_to_head_page(buf);
> -               put_page(page);
> +               virtnet_put_page(rq, page, true);
>         }
>  }
>
> @@ -2253,7 +2194,7 @@ static int virtnet_build_xdp_buff_mrg(struct net_device *dev,
>                 offset = buf - page_address(page);
>
>                 if (check_mergeable_len(dev, ctx, len)) {
> -                       put_page(page);
> +                       virtnet_put_page(rq, page, true);
>                         goto err;
>                 }
>
> @@ -2272,7 +2213,7 @@ static int virtnet_build_xdp_buff_mrg(struct net_device *dev,
>         return 0;
>
>  err:
> -       put_xdp_frags(xdp);
> +       put_xdp_frags(xdp, rq);
>         return -EINVAL;
>  }
>
> @@ -2337,7 +2278,7 @@ static void *mergeable_xdp_get_buf(struct virtnet_info *vi,
>                 if (*len + xdp_room > PAGE_SIZE)
>                         return NULL;
>
> -               xdp_page = alloc_page(GFP_ATOMIC);
> +               xdp_page = page_pool_alloc_pages(rq->page_pool, GFP_ATOMIC);
>                 if (!xdp_page)
>                         return NULL;
>
> @@ -2347,7 +2288,7 @@ static void *mergeable_xdp_get_buf(struct virtnet_info *vi,
>
>         *frame_sz = PAGE_SIZE;
>
> -       put_page(*page);
> +       virtnet_put_page(rq, *page, true);
>
>         *page = xdp_page;
>
> @@ -2393,6 +2334,8 @@ static struct sk_buff *receive_mergeable_xdp(struct net_device *dev,
>                 head_skb = build_skb_from_xdp_buff(dev, vi, &xdp, xdp_frags_truesz);
>                 if (unlikely(!head_skb))
>                         break;
> +
> +               skb_mark_for_recycle(head_skb);
>                 return head_skb;
>
>         case XDP_TX:
> @@ -2403,10 +2346,10 @@ static struct sk_buff *receive_mergeable_xdp(struct net_device *dev,
>                 break;
>         }
>
> -       put_xdp_frags(&xdp);
> +       put_xdp_frags(&xdp, rq);
>
>  err_xdp:
> -       put_page(page);
> +       virtnet_put_page(rq, page, true);
>         mergeable_buf_free(rq, num_buf, dev, stats);
>
>         u64_stats_inc(&stats->xdp_drops);
> @@ -2414,7 +2357,8 @@ static struct sk_buff *receive_mergeable_xdp(struct net_device *dev,
>         return NULL;
>  }
>
> -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)
> @@ -2446,7 +2390,7 @@ static struct sk_buff *virtnet_skb_append_frag(struct sk_buff *head_skb,
>
>         offset = buf - page_address(page);
>         if (skb_can_coalesce(curr_skb, num_skb_frags, page, offset)) {
> -               put_page(page);
> +               virtnet_put_page(rq, page, true);
>                 skb_coalesce_rx_frag(curr_skb, num_skb_frags - 1,
>                                      len, truesize);
>         } else {
> @@ -2499,6 +2443,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>
>         if (unlikely(!curr_skb))
>                 goto err_skb;
> +
> +       skb_mark_for_recycle(head_skb);
>         while (--num_buf) {
>                 buf = virtnet_rq_get_buf(rq, &len, &ctx);
>                 if (unlikely(!buf)) {
> @@ -2517,7 +2463,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>                         goto err_skb;
>
>                 truesize = mergeable_ctx_to_truesize(ctx);
> -               curr_skb  = virtnet_skb_append_frag(head_skb, curr_skb, page,
> +               curr_skb  = virtnet_skb_append_frag(rq, head_skb, curr_skb, page,
>                                                     buf, len, truesize);
>                 if (!curr_skb)
>                         goto err_skb;
> @@ -2527,7 +2473,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>         return head_skb;
>
>  err_skb:
> -       put_page(page);
> +       virtnet_put_page(rq, page, true);
>         mergeable_buf_free(rq, num_buf, dev, stats);
>
>  err_buf:
> @@ -2666,32 +2612,42 @@ static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
>  static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
>                              gfp_t gfp)
>  {
> -       char *buf;
>         unsigned int xdp_headroom = virtnet_get_headroom(vi);
>         void *ctx = (void *)(unsigned long)xdp_headroom;
>         int len = vi->hdr_len + VIRTNET_RX_PAD + GOOD_PACKET_LEN + xdp_headroom;
> +       unsigned int offset;
> +       struct page *page;
> +       dma_addr_t addr;
> +       char *buf;
>         int err;
>
>         len = SKB_DATA_ALIGN(len) +
>               SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
>
> -       if (unlikely(!skb_page_frag_refill(len, &rq->alloc_frag, gfp)))
> -               return -ENOMEM;
> -
> -       buf = virtnet_rq_alloc(rq, len, gfp);
> -       if (unlikely(!buf))
> +       page = page_pool_alloc_frag(rq->page_pool, &offset, len, gfp);
> +       if (unlikely(!page))
>                 return -ENOMEM;
>
> +       buf = page_address(page) + offset;
>         buf += VIRTNET_RX_PAD + xdp_headroom;
>
> -       virtnet_rq_init_one_sg(rq, buf, vi->hdr_len + GOOD_PACKET_LEN);
> +       if (rq->use_page_pool_dma) {
> +               addr = page_pool_get_dma_addr(page) + offset;
> +               addr += VIRTNET_RX_PAD + xdp_headroom;
>
> -       err = virtqueue_add_inbuf_premapped(rq->vq, rq->sg, 1, buf, ctx, gfp);
> -       if (err < 0) {
> -               virtnet_rq_unmap(rq, buf, 0);
> -               put_page(virt_to_head_page(buf));
> +               sg_init_table(rq->sg, 1);
> +               sg_fill_dma(rq->sg, addr, vi->hdr_len + GOOD_PACKET_LEN);
> +               err = virtqueue_add_inbuf_premapped(rq->vq, rq->sg, 1,
> +                                                   buf, ctx, gfp);
> +       } else {
> +               sg_init_one(rq->sg, buf, vi->hdr_len + GOOD_PACKET_LEN);
> +               err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1,
> +                                             buf, ctx, gfp);
>         }
>
> +       if (err < 0)
> +               page_pool_put_page(rq->page_pool, virt_to_head_page(buf),
> +                                  -1, false);
>         return err;
>  }
>
> @@ -2764,13 +2720,15 @@ static unsigned int get_mergeable_buf_len(struct receive_queue *rq,
>  static int add_recvbuf_mergeable(struct virtnet_info *vi,
>                                  struct receive_queue *rq, gfp_t gfp)
>  {
> -       struct page_frag *alloc_frag = &rq->alloc_frag;
>         unsigned int headroom = virtnet_get_headroom(vi);
>         unsigned int tailroom = headroom ? sizeof(struct skb_shared_info) : 0;
>         unsigned int room = SKB_DATA_ALIGN(headroom + tailroom);
>         unsigned int len, hole;
> -       void *ctx;
> +       unsigned int offset;
> +       struct page *page;
> +       dma_addr_t addr;
>         char *buf;
> +       void *ctx;
>         int err;
>
>         /* Extra tailroom is needed to satisfy XDP's assumption. This
> @@ -2779,18 +2737,14 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
>          */
>         len = get_mergeable_buf_len(rq, &rq->mrg_avg_pkt_len, room);
>
> -       if (unlikely(!skb_page_frag_refill(len + room, alloc_frag, gfp)))
> -               return -ENOMEM;
> -
> -       if (!alloc_frag->offset && len + room + sizeof(struct virtnet_rq_dma) > alloc_frag->size)
> -               len -= sizeof(struct virtnet_rq_dma);
> -
> -       buf = virtnet_rq_alloc(rq, len + room, gfp);
> -       if (unlikely(!buf))
> +       page = page_pool_alloc_frag(rq->page_pool, &offset, len + room, gfp);
> +       if (unlikely(!page))
>                 return -ENOMEM;
>
> +       buf = page_address(page) + offset;
>         buf += headroom; /* advance address leaving hole at front of pkt */
> -       hole = alloc_frag->size - alloc_frag->offset;
> +
> +       hole = PAGE_SIZE - (offset + len + room);
>         if (hole < len + room) {
>                 /* To avoid internal fragmentation, if there is very likely not
>                  * enough space for another buffer, add the remaining space to
> @@ -2800,18 +2754,27 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
>                  */
>                 if (!headroom)
>                         len += hole;
> -               alloc_frag->offset += hole;
>         }
>
> -       virtnet_rq_init_one_sg(rq, buf, len);
> -
>         ctx = mergeable_len_to_ctx(len + room, headroom);
> -       err = virtqueue_add_inbuf_premapped(rq->vq, rq->sg, 1, buf, ctx, gfp);
> -       if (err < 0) {
> -               virtnet_rq_unmap(rq, buf, 0);
> -               put_page(virt_to_head_page(buf));
> +
> +       if (rq->use_page_pool_dma) {
> +               addr = page_pool_get_dma_addr(page) + offset;
> +               addr += headroom;
> +
> +               sg_init_table(rq->sg, 1);
> +               sg_fill_dma(rq->sg, addr, len);
> +               err = virtqueue_add_inbuf_premapped(rq->vq, rq->sg, 1,
> +                                                   buf, ctx, gfp);
> +       } else {
> +               sg_init_one(rq->sg, buf, len);
> +               err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1,
> +                                             buf, ctx, gfp);
>         }
>
> +       if (err < 0)
> +               page_pool_put_page(rq->page_pool, virt_to_head_page(buf),
> +                                  -1, false);
>         return err;
>  }
>
> @@ -3128,7 +3091,10 @@ static int virtnet_enable_queue_pair(struct virtnet_info *vi, int qp_index)
>                 return err;
>
>         err = xdp_rxq_info_reg_mem_model(&vi->rq[qp_index].xdp_rxq,
> -                                        MEM_TYPE_PAGE_SHARED, NULL);
> +                                        vi->rq[qp_index].page_pool ?
> +                                               MEM_TYPE_PAGE_POOL :
> +                                               MEM_TYPE_PAGE_SHARED,
> +                                        vi->rq[qp_index].page_pool);
>         if (err < 0)
>                 goto err_xdp_reg_mem_model;
>
> @@ -3168,6 +3134,81 @@ static void virtnet_update_settings(struct virtnet_info *vi)
>                 vi->duplex = duplex;
>  }
>
> +static int virtnet_create_page_pools(struct virtnet_info *vi)
> +{
> +       int i, err;
> +
> +       for (i = 0; i < vi->max_queue_pairs; i++) {
> +               struct receive_queue *rq = &vi->rq[i];
> +               struct page_pool_params pp_params = { 0 };
> +               struct device *dma_dev;
> +
> +               if (rq->page_pool)
> +                       continue;
> +
> +               if (rq->xsk_pool)
> +                       continue;
> +
> +               if (!vi->mergeable_rx_bufs && vi->big_packets)
> +                       continue;

This check could be moved out of the loop.

> +
> +               pp_params.order = 0;
> +               pp_params.pool_size = virtqueue_get_vring_size(rq->vq);
> +               pp_params.nid = dev_to_node(vi->vdev->dev.parent);
> +               pp_params.netdev = vi->dev;
> +               pp_params.napi = &rq->napi;
> +
> +               /* Check if backend supports DMA API (e.g., vhost, virtio-pci).
> +                * If so, use page_pool's DMA mapping for premapped buffers.
> +                * Otherwise (e.g., VDUSE), page_pool only handles allocation.
> +                */
> +               dma_dev = virtqueue_dma_dev(rq->vq);
> +               if (dma_dev) {
> +                       pp_params.dev = dma_dev;
> +                       pp_params.flags = PP_FLAG_DMA_MAP;
> +                       pp_params.dma_dir = DMA_FROM_DEVICE;
> +                       rq->use_page_pool_dma = true;
> +               } else {
> +                       pp_params.dev = vi->vdev->dev.parent;
> +                       pp_params.flags = 0;
> +                       rq->use_page_pool_dma = false;
> +               }
> +
> +               rq->page_pool = page_pool_create(&pp_params);
> +               if (IS_ERR(rq->page_pool)) {
> +                       err = PTR_ERR(rq->page_pool);
> +                       rq->page_pool = NULL;
> +                       goto err_cleanup;
> +               }
> +       }
> +       return 0;
> +
> +err_cleanup:
> +       while (--i >= 0) {
> +               struct receive_queue *rq = &vi->rq[i];
> +
> +               if (rq->page_pool) {
> +                       page_pool_destroy(rq->page_pool);
> +                       rq->page_pool = NULL;
> +               }
> +       }
> +       return err;
> +}
> +
> +static void virtnet_destroy_page_pools(struct virtnet_info *vi)
> +{
> +       int i;
> +
> +       for (i = 0; i < vi->max_queue_pairs; i++) {
> +               struct receive_queue *rq = &vi->rq[i];
> +
> +               if (rq->page_pool) {
> +                       page_pool_destroy(rq->page_pool);
> +                       rq->page_pool = NULL;
> +               }
> +       }
> +}
> +
>  static int virtnet_open(struct net_device *dev)
>  {
>         struct virtnet_info *vi = netdev_priv(dev);
> @@ -3770,7 +3811,6 @@ static int virtnet_close(struct net_device *dev)
>          * open
>          */
>         cancel_work_sync(&vi->config_work);
> -

Unnecessary changes.

>         for (i = 0; i < vi->max_queue_pairs; i++) {
>                 virtnet_disable_queue_pair(vi, i);
>                 virtnet_cancel_dim(vi, &vi->rq[i].dim);
> @@ -6442,9 +6482,6 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
>                 vi->sq[i].vq = vqs[txq2vq(i)];
>         }
>
> -       /* run here: ret == 0. */
> -
> -

Seems some leftovers of some temporary change.

>  err_find:
>         kfree(ctx);
>  err_ctx:
> @@ -6945,6 +6982,14 @@ static int virtnet_probe(struct virtio_device *vdev)
>                         goto free;
>         }
>
> +       /* Create page pools for receive queues.
> +        * Page pools are created at probe time so they can be used
> +        * with premapped DMA addresses throughout the device lifetime.
> +        */
> +       err = virtnet_create_page_pools(vi);
> +       if (err)
> +               goto free_irq_moder;
> +
>  #ifdef CONFIG_SYSFS
>         if (vi->mergeable_rx_bufs)
>                 dev->sysfs_rx_queue_group = &virtio_net_mrg_rx_group;
> @@ -6958,7 +7003,7 @@ static int virtnet_probe(struct virtio_device *vdev)
>                 vi->failover = net_failover_create(vi->dev);
>                 if (IS_ERR(vi->failover)) {
>                         err = PTR_ERR(vi->failover);
> -                       goto free_vqs;
> +                       goto free_page_pools;
>                 }
>         }
>
> @@ -7075,7 +7120,10 @@ static int virtnet_probe(struct virtio_device *vdev)
>         unregister_netdev(dev);
>  free_failover:
>         net_failover_destroy(vi->failover);
> -free_vqs:
> +free_page_pools:
> +       virtnet_destroy_page_pools(vi);
> +free_irq_moder:
> +       virtnet_free_irq_moder(vi);
>         virtio_reset_device(vdev);
>         free_receive_page_frags(vi);
>         virtnet_del_vqs(vi);
> @@ -7104,6 +7152,8 @@ static void remove_vq_common(struct virtnet_info *vi)
>
>         free_receive_page_frags(vi);
>
> +       virtnet_destroy_page_pools(vi);
> +
>         virtnet_del_vqs(vi);
>  }
>
> --
> 2.47.3
>

Thanks

[PATCH net-next v3 2/2] selftests: virtio_net: add buffer circulation test

[Vishwanath Seshagiri]

Add iperf3-based test to verify RX buffer handling under load.
Optionally logs page_pool tracepoints when available.

Signed-off-by: Vishwanath Seshagiri <vishs@meta.com>
---
 .../drivers/net/virtio_net/basic_features.sh  | 86 +++++++++++++++++++
 1 file changed, 86 insertions(+)

diff --git a/tools/testing/selftests/drivers/net/virtio_net/basic_features.sh b/tools/testing/selftests/drivers/net/virtio_net/basic_features.sh
index cf8cf816ed48..fa98505c4674 100755
--- a/tools/testing/selftests/drivers/net/virtio_net/basic_features.sh
+++ b/tools/testing/selftests/drivers/net/virtio_net/basic_features.sh
@@ -6,6 +6,7 @@
 ALL_TESTS="
 	initial_ping_test
 	f_mac_test
+	buffer_circulation_test
 "
 
 source virtio_net_common.sh
@@ -16,6 +17,8 @@ source "$lib_dir"/../../../net/forwarding/lib.sh
 h1=${NETIFS[p1]}
 h2=${NETIFS[p2]}
 
+IPERF_SERVER_PID=""
+
 h1_create()
 {
 	simple_if_init $h1 $H1_IPV4/24 $H1_IPV6/64
@@ -83,6 +86,84 @@ f_mac_test()
 	log_test "$test_name"
 }
 
+buffer_circulation_test()
+{
+	RET=0
+	local test_name="buffer circulation"
+	local tracefs="/sys/kernel/tracing"
+
+	if ! check_command iperf3; then
+		log_test_skip "$test_name" "iperf3 not installed"
+		return 0
+	fi
+
+	setup_cleanup
+	setup_prepare
+
+	ping -c 1 -I "$h1" "$H2_IPV4" >/dev/null
+	if [ $? -ne 0 ]; then
+		check_err 1 "Ping failed"
+		log_test "$test_name"
+		return
+	fi
+
+	local rx_start=$(cat /sys/class/net/"$h2"/statistics/rx_packets)
+	local tx_start=$(cat /sys/class/net/"$h1"/statistics/tx_packets)
+
+	if [ -d "$tracefs/events/page_pool" ]; then
+		echo > "$tracefs/trace"
+		echo 1 > "$tracefs/events/page_pool/enable"
+	fi
+
+	local port=$(shuf -i 49152-65535 -n 1)
+
+	iperf3 -s -1 --bind-dev "$h2" -p "$port" &>/dev/null &
+	IPERF_SERVER_PID=$!
+	sleep 1
+
+	if ! kill -0 "$IPERF_SERVER_PID" 2>/dev/null; then
+		IPERF_SERVER_PID=""
+		if [ -d "$tracefs/events/page_pool" ]; then
+			echo 0 > "$tracefs/events/page_pool/enable"
+		fi
+		check_err 1 "iperf3 server died"
+		log_test "$test_name"
+		return
+	fi
+
+	iperf3 -c "$H2_IPV4" --bind-dev "$h1" -p "$port" -t 5 >/dev/null 2>&1
+	local iperf_ret=$?
+
+	if [ -n "$IPERF_SERVER_PID" ]; then
+		kill "$IPERF_SERVER_PID" 2>/dev/null || true
+		wait "$IPERF_SERVER_PID" 2>/dev/null || true
+		IPERF_SERVER_PID=""
+	fi
+
+	if [ -d "$tracefs/events/page_pool" ]; then
+		echo 0 > "$tracefs/events/page_pool/enable"
+		local trace="$tracefs/trace"
+		local hold=$(grep -c "page_pool_state_hold" "$trace" 2>/dev/null)
+		local release=$(grep -c "page_pool_state_release" "$trace" 2>/dev/null)
+		log_info "page_pool events: hold=${hold:-0}, release=${release:-0}"
+	fi
+
+	local rx_end=$(cat /sys/class/net/"$h2"/statistics/rx_packets)
+	local tx_end=$(cat /sys/class/net/"$h1"/statistics/tx_packets)
+	local rx_delta=$((rx_end - rx_start))
+	local tx_delta=$((tx_end - tx_start))
+
+	log_info "Circulated TX:$tx_delta RX:$rx_delta"
+
+	if [ "$iperf_ret" -ne 0 ]; then
+		check_err 1 "iperf3 failed"
+	elif [ "$rx_delta" -lt 10000 ]; then
+		check_err 1 "Too few packets: $rx_delta"
+	fi
+
+	log_test "$test_name"
+}
+
 setup_prepare()
 {
 	virtio_device_rebind $h1
@@ -113,6 +194,11 @@ setup_cleanup()
 
 cleanup()
 {
+	if [ -n "$IPERF_SERVER_PID" ]; then
+		kill "$IPERF_SERVER_PID" 2>/dev/null || true
+		wait "$IPERF_SERVER_PID" 2>/dev/null || true
+	fi
+
 	pre_cleanup
 	setup_cleanup
 }
-- 
2.47.3