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Message-ID: <1770621144.341019-1-xuanzhuo@linux.alibaba.com>
Date: Mon, 9 Feb 2026 15:12:24 +0800
From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To: Vishwanath Seshagiri <vishs@...a.com>
Cc: Eugenio Pérez <eperezma@...hat.com>,
Andrew Lunn <andrew+netdev@...n.ch>,
"David S . Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
David Wei <dw@...idwei.uk>,
Matteo Croce <technoboy85@...il.com>,
Ilias Apalodimas <ilias.apalodimas@...aro.org>,
netdev@...r.kernel.org,
virtualization@...ts.linux.dev,
linux-kernel@...r.kernel.org,
kernel-team@...a.com,
"Michael S . Tsirkin" <mst@...hat.com>,
Jason Wang <jasowang@...hat.com>
Subject: Re: [PATCH v6] virtio_net: add page_pool support for buffer allocation
On Sun, 8 Feb 2026 18:42:26 -0800, Vishwanath Seshagiri <vishs@...a.com> wrote:
> On 2/8/26 6:00 PM, Xuan Zhuo wrote:
> > On Sun, 8 Feb 2026 09:54:10 -0800, Vishwanath Seshagiri <vishs@...a.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@...a.com>
> >> ---
> >> Changes in v6:
> >> - Drop page_pool_frag_offset_add() helper and switch to page_pool_alloc_va();
> >> page_pool_alloc_netmem() already handles internal fragmentation internally
> >> (Jakub Kicinski)
> >> - v5:
> >> https://lore.kernel.org/virtualization/20260206002715.1885869-1-vishs@meta.com/
> >>
> >> Benchmark results:
> >>
> >> Configuration: pktgen TX -> tap -> vhost-net | virtio-net RX -> XDP_DROP
> >>
> >> Small packets (64 bytes, mrg_rxbuf=off):
> >> 1Q: 853,493 -> 868,923 pps (+1.8%)
> >> 2Q: 1,655,793 -> 1,696,707 pps (+2.5%)
> >> 4Q: 3,143,375 -> 3,302,511 pps (+5.1%)
> >> 8Q: 6,082,590 -> 6,156,894 pps (+1.2%)
> >>
> >> Mergeable RX (64 bytes):
> >> 1Q: 766,168 -> 814,493 pps (+6.3%)
> >> 2Q: 1,384,871 -> 1,670,639 pps (+20.6%)
> >> 4Q: 2,773,081 -> 3,080,574 pps (+11.1%)
> >> 8Q: 5,600,615 -> 6,043,891 pps (+7.9%)
> >>
> >> Mergeable RX (1500 bytes):
> >> 1Q: 741,579 -> 785,442 pps (+5.9%)
> >> 2Q: 1,310,043 -> 1,534,554 pps (+17.1%)
> >> 4Q: 2,748,700 -> 2,890,582 pps (+5.2%)
> >> 8Q: 5,348,589 -> 5,618,664 pps (+5.0%)
> >>
> >> drivers/net/Kconfig | 1 +
> >> drivers/net/virtio_net.c | 434 +++++++++++++++++++--------------------
> >> 2 files changed, 217 insertions(+), 218 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..5055df56e4a7 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);
> >> +}
> >
> > Why we need this?
> > For the caller, we should know which one should be used?
> >
>
> This was after some feedback to unify the alloc/free path checks in v4.
> But you raise a valid point - callers already know the mode via
> virtnet_no_page_pool(). I can simplify this to just call
> page_pool_put_page() directly, since virtnet_put_page() is only called
> from paths that already checked we're using page_pool. Would you prefer
> that?
Based on my understanding, the big mode should directly call the Page API, while
all other modes should directly call the PP API. Therefore, I believe it's
better for each mode to directly invoke its respective API.
>
>
> >
> >> +
> >> 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 +2582,41 @@ 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 len = vi->hdr_len + VIRTNET_RX_PAD + GOOD_PACKET_LEN + xdp_headroom;
> >> + 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);
> >> + buf = page_pool_alloc_va(rq->page_pool, &len, gfp);
> >> if (unlikely(!buf))
> >> return -ENOMEM;
> >>
> >> 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) {
> >> + page = virt_to_head_page(buf);
> >> + addr = page_pool_get_dma_addr(page) +
> >> + (buf - (char *)page_address(page));
> >>
> >> - 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 +2689,14 @@ 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 len, alloc_len;
> >> + struct page *page;
> >> + dma_addr_t addr;
> >> char *buf;
> >> + void *ctx;
> >> int err;
> >>
> >> /* Extra tailroom is needed to satisfy XDP's assumption. This
> >> @@ -2779,39 +2705,36 @@ 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);
> >> + alloc_len = len + room;
> >> + buf = page_pool_alloc_va(rq->page_pool, &alloc_len, gfp);
> >> if (unlikely(!buf))
> >> return -ENOMEM;
> >>
> >> buf += headroom; /* advance address leaving hole at front of pkt */
> >> - hole = alloc_frag->size - alloc_frag->offset;
> >> - if (hole < len + room) {
> >> - /* To avoid internal fragmentation, if there is very likely not
> >> - * enough space for another buffer, add the remaining space to
> >> - * the current buffer.
> >> - * 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)
> >> - len += hole;
> >> - alloc_frag->offset += hole;
> >> - }
> >>
> >> - virtnet_rq_init_one_sg(rq, buf, len);
> >> + if (!headroom)
> >> + len = alloc_len - room;
> >>
> >> 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) {
> >> + page = virt_to_head_page(buf);
> >> + addr = page_pool_get_dma_addr(page) +
> >> + (buf - (char *)page_address(page));
> >> +
> >> + 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 +3051,10 @@ 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 +3094,81 @@ 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;
> >
> > Can the page pool handles dma with vi->vdev->dev.parent?
>
> No, we cannot use the page_pool DMA with vi->vdev->dev.parent in VDUSE
> case because VDUSE uses its own address translation. virtqueue_dma_dev()
> returns NULL, virtio doesn't use standard DMA API at all. Now that I
> think about it, setting pp_params.dev in this branch is unnecessary
> since it is never accessed. I can remove it, if you prefer.
If that's the case, then it is indeed a bit troublesome. I don't know if VDUSE
has a better solution. What I don't like is use_page_pool_dma -- it
introduces many branches into the code, making it more chaotic. We may need to
look for a better unified solution.
Thanks.
>
>
> >
> > Thanks.
> >
> >> + }
> >> +
> >> + 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 +6288,6 @@ 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 +6431,8 @@ 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 +6933,14 @@ 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 +6954,7 @@ 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 +7071,11 @@ 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 +7100,7 @@ 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
> >>
>
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