[PATCH net-next v5 0/2] virtio_net: add page_pool support

[PATCH net-next v5 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 v5
=============

Addressing reviewer feedback from v4:

- Add page_pool_frag_offset_add() helper to page_pool API to advance
  fragment offset when drivers extend buffers to consume unused page
  space (hole optimization). (Michael S. Tsirkin)
- Unify big_packets condition checks and added an  explanatory comment 
  (Michael S. Tsirkin)
- Add page_pool_dma_sync_for_cpu() calls in receive paths before
  reading buffer data when using PP_FLAG_DMA_MAP
  (Michael S. Tsirkin)
- Remove virtnet_rq_unmap() and free_receive_page_frags() entirely,
  replacing with page_pool lifecycle management (Jason Wang)
- Dropped selftests patch from the series
- v4 link: https://lore.kernel.org/virtualization/20260204193617.1200752-1-vishs@meta.com/ 

Changes in v4
=============

Addressing reviewer feedback from v3:

- Remove unnecessary !rq->page_pool check in page_to_skb()
- Reorder put_xdp_frags() parameters
- Remove unnecessary xdp_page = NULL initialization in receive_small_xdp()
- Move big_packets mode check outside the loop in virtnet_create_page_pools()
  for efficiency
- Remove unrelated whitespace changes
- v3 link: https://lore.kernel.org/virtualization/20260203231021.1331392-1-vishs@meta.com/

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):
  page_pool: add page_pool_frag_offset_add() helper
  virtio_net: add page_pool support for buffer allocation

 drivers/net/Kconfig             |   1 +
 drivers/net/virtio_net.c        | 430 ++++++++++++++++----------------
 include/net/page_pool/helpers.h |  20 ++
 3 files changed, 241 insertions(+), 210 deletions(-)

-- 
2.47.3

[PATCH net-next v5 1/2] page_pool: add page_pool_frag_offset_add() helper

[Vishwanath Seshagiri]

Add a helper function to advance the fragment offset without performing
an allocation. This is needed by drivers that extend a buffer to consume
unused space at the end of a page fragment to avoid internal fragmentation.

When a driver uses page_pool_alloc_frag() and determines that the
remaining space in the page is too small for another buffer, it may
extend the current buffer to include that space. However, page_pool's
internal frag_offset is not aware of this extension, which could cause
the next allocation to overlap with the extended buffer.

page_pool_frag_offset_add() allows drivers to advance frag_offset to
match the actual consumed space.

Signed-off-by: Vishwanath Seshagiri <vishs@meta.com>
---
 include/net/page_pool/helpers.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index 3247026e096a..14907c3badae 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -96,6 +96,26 @@ static inline struct page *page_pool_dev_alloc_pages(struct page_pool *pool)
 	return page_pool_alloc_pages(pool, gfp);
 }
 
+/**
+ * page_pool_frag_offset_add() - advance fragment offset without allocation
+ * @pool: pool to update
+ * @bytes: number of bytes to skip
+ *
+ * Advance the fragment offset by @bytes without performing an allocation.
+ * This is useful when a driver extends a buffer to consume unused space
+ * at the end of a page fragment (to avoid internal fragmentation), and
+ * needs to ensure the next allocation doesn't overlap.
+ *
+ * Must be called in the same context as page_pool_alloc_frag() to avoid
+ * racing with fragment allocations.
+ *
+ */
+static inline void page_pool_frag_offset_add(struct page_pool *pool,
+					     unsigned int bytes)
+{
+	pool->frag_offset += bytes;
+}
+
 /**
  * page_pool_dev_alloc_frag() - allocate a page fragment.
  * @pool: pool from which to allocate
-- 
2.47.3

[PATCH net-next v5 2/2] 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 | 430 ++++++++++++++++++++-------------------
 2 files changed, 221 insertions(+), 210 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..caf26615787a 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);
@@ -290,14 +291,6 @@ struct virtnet_interrupt_coalesce {
 	u32 max_usecs;
 };
 
-/* The dma information of pages allocated at a time. */
-struct virtnet_rq_dma {
-	dma_addr_t addr;
-	u32 ref;
-	u16 len;
-	u16 need_sync;
-};
-
 /* Internal representation of a send virtqueue */
 struct send_queue {
 	/* Virtqueue associated with this send _queue */
@@ -356,8 +349,10 @@ struct receive_queue {
 	/* Average packet length for mergeable receive buffers. */
 	struct ewma_pkt_len mrg_avg_pkt_len;
 
-	/* 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];
@@ -370,9 +365,6 @@ struct receive_queue {
 
 	struct xdp_rxq_info xdp_rxq;
 
-	/* Record the last dma info to free after new pages is allocated. */
-	struct virtnet_rq_dma *last_dma;
-
 	struct xsk_buff_pool *xsk_pool;
 
 	/* xdp rxq used by xsk */
@@ -521,11 +513,13 @@ 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 +700,24 @@ 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)
@@ -876,10 +879,16 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
 		skb = virtnet_build_skb(buf, truesize, p - buf, len);
 		if (unlikely(!skb))
 			return NULL;
+		/* Big packets mode chains pages via page->private, which is
+		 * incompatible with the way page_pool uses page->private.
+		 * Currently, big packets mode doesn't use page pools.
+		 */
+		if (vi->big_packets && !vi->mergeable_rx_bufs) {
+			page = (struct page *)page->private;
+			if (page)
+				give_pages(rq, page);
+		}
 
-		page = (struct page *)page->private;
-		if (page)
-			give_pages(rq, page);
 		goto ok;
 	}
 
@@ -925,133 +934,18 @@ 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;
 }
 
-static void virtnet_rq_unmap(struct receive_queue *rq, void *buf, u32 len)
-{
-	struct virtnet_info *vi = rq->vq->vdev->priv;
-	struct page *page = virt_to_head_page(buf);
-	struct virtnet_rq_dma *dma;
-	void *head;
-	int offset;
-
-	BUG_ON(vi->big_packets && !vi->mergeable_rx_bufs);
-
-	head = page_address(page);
-
-	dma = head;
-
-	--dma->ref;
-
-	if (dma->need_sync && len) {
-		offset = buf - (head + sizeof(*dma));
-
-		virtqueue_map_sync_single_range_for_cpu(rq->vq, dma->addr,
-							offset, len,
-							DMA_FROM_DEVICE);
-	}
-
-	if (dma->ref)
-		return;
-
-	virtqueue_unmap_single_attrs(rq->vq, dma->addr, dma->len,
-				     DMA_FROM_DEVICE, DMA_ATTR_SKIP_CPU_SYNC);
-	put_page(page);
-}
-
 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 +961,6 @@ 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 +1226,7 @@ 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 +1662,7 @@ 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 receive_queue *rq, struct xdp_buff *xdp)
 {
 	struct skb_shared_info *shinfo;
 	struct page *xdp_page;
@@ -1781,7 +1672,7 @@ 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 +1764,7 @@ 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 +1788,7 @@ 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 +1796,21 @@ 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;
 }
 
@@ -1969,6 +1860,12 @@ static struct sk_buff *receive_small_xdp(struct net_device *dev,
 	unsigned int metasize = 0;
 	u32 act;
 
+	if (rq->use_page_pool_dma) {
+		int off = buf - page_address(page);
+
+		page_pool_dma_sync_for_cpu(rq->page_pool, page, off, len);
+	}
+
 	if (unlikely(hdr->hdr.gso_type))
 		goto err_xdp;
 
@@ -1996,7 +1893,7 @@ 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 +1925,15 @@ 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;
 }
@@ -2056,6 +1955,12 @@ static struct sk_buff *receive_small(struct net_device *dev,
 	 */
 	buf -= VIRTNET_RX_PAD + xdp_headroom;
 
+	if (rq->use_page_pool_dma) {
+		int offset = buf - page_address(page);
+
+		page_pool_dma_sync_for_cpu(rq->page_pool, page, offset, len);
+	}
+
 	len -= vi->hdr_len;
 	u64_stats_add(&stats->bytes, len);
 
@@ -2082,12 +1987,14 @@ 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 +2049,7 @@ 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 +2160,7 @@ 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 +2179,7 @@ static int virtnet_build_xdp_buff_mrg(struct net_device *dev,
 	return 0;
 
 err:
-	put_xdp_frags(xdp);
+	put_xdp_frags(rq, xdp);
 	return -EINVAL;
 }
 
@@ -2337,7 +2244,7 @@ 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 +2254,7 @@ 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 +2300,8 @@ 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 +2312,10 @@ static struct sk_buff *receive_mergeable_xdp(struct net_device *dev,
 		break;
 	}
 
-	put_xdp_frags(&xdp);
+	put_xdp_frags(rq, &xdp);
 
 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 +2323,8 @@ 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 +2356,7 @@ 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 {
@@ -2475,6 +2385,10 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 	unsigned int headroom = mergeable_ctx_to_headroom(ctx);
 
 	head_skb = NULL;
+
+	if (rq->use_page_pool_dma)
+		page_pool_dma_sync_for_cpu(rq->page_pool, page, offset, len);
+
 	u64_stats_add(&stats->bytes, len - vi->hdr_len);
 
 	if (check_mergeable_len(dev, ctx, len))
@@ -2499,6 +2413,8 @@ 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 +2433,7 @@ 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 +2443,7 @@ 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 +2582,42 @@ 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 +2690,15 @@ 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 +2707,14 @@ 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
@@ -2798,20 +2722,31 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
 		 * XDP core assumes that frame_size of xdp_buff and the length
 		 * of the frag are PAGE_SIZE, so we disable the hole mechanism.
 		 */
-		if (!headroom)
+		if (!headroom) {
 			len += hole;
-		alloc_frag->offset += hole;
+			page_pool_frag_offset_add(rq->page_pool, 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 +3063,10 @@ 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 +3106,81 @@ 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;
+
+	if (!vi->mergeable_rx_bufs && vi->big_packets)
+		return 0;
+
+	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;
+
+		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);
@@ -6287,17 +6300,6 @@ static void free_receive_bufs(struct virtnet_info *vi)
 	rtnl_unlock();
 }
 
-static void free_receive_page_frags(struct virtnet_info *vi)
-{
-	int i;
-	for (i = 0; i < vi->max_queue_pairs; i++)
-		if (vi->rq[i].alloc_frag.page) {
-			if (vi->rq[i].last_dma)
-				virtnet_rq_unmap(&vi->rq[i], vi->rq[i].last_dma, 0);
-			put_page(vi->rq[i].alloc_frag.page);
-		}
-}
-
 static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf)
 {
 	struct virtnet_info *vi = vq->vdev->priv;
@@ -6441,10 +6443,8 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
 		vi->rq[i].min_buf_len = mergeable_min_buf_len(vi, vi->rq[i].vq);
 		vi->sq[i].vq = vqs[txq2vq(i)];
 	}
-
 	/* run here: ret == 0. */
 
-
 err_find:
 	kfree(ctx);
 err_ctx:
@@ -6945,6 +6945,14 @@ 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 +6966,7 @@ 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;
 		}
 	}
 
@@ -7075,9 +7083,11 @@ 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);
 free:
 	free_netdev(dev);
@@ -7102,7 +7112,7 @@ static void remove_vq_common(struct virtnet_info *vi)
 
 	free_receive_bufs(vi);
 
-	free_receive_page_frags(vi);
+	virtnet_destroy_page_pools(vi);
 
 	virtnet_del_vqs(vi);
 }
-- 
2.47.3

Re: [PATCH net-next v5 2/2] virtio_net: add page_pool support for buffer allocation

[Jakub Kicinski]

On Thu, 5 Feb 2026 16:27:15 -0800 Vishwanath Seshagiri wrote:
> +	page = page_pool_alloc_frag(rq->page_pool, &offset, len + room, gfp);
> +	if (unlikely(!page))
>  		return -ENOMEM;
>  
> +	buf = page_address(page) + offset;

Please take a look at page_pool_alloc_va()

I mean all the way down until you reach page_pool_alloc_netmem()
and realize the helper you're adding in patch 1 is a solved problem
-- 
pw-bot: cr

Re: [PATCH net-next v5 2/2] virtio_net: add page_pool support for buffer allocation

[Vishwanath Seshagiri]

On 2/6/26 8:41 PM, Jakub Kicinski wrote:
> On Thu, 5 Feb 2026 16:27:15 -0800 Vishwanath Seshagiri wrote:
>> +	page = page_pool_alloc_frag(rq->page_pool, &offset, len + room, gfp);
>> +	if (unlikely(!page))
>>   		return -ENOMEM;
>>   
>> +	buf = page_address(page) + offset;
> 
> Please take a look at page_pool_alloc_va()
> 
> I mean all the way down until you reach page_pool_alloc_netmem()
> and realize the helper you're adding in patch 1 is a solved problem

I apologize for adding patch 1. I will use page_pool_alloc_va and send
v6 with only patch 2.