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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , David Wei , Matteo Croce , Ilias Apalodimas , netdev@vger.kernel.org, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, kernel-team@meta.com References: <20260208175410.1910001-1-vishs@meta.com> <20260208131355-mutt-send-email-mst@kernel.org> Content-Language: en-US From: Vishwanath Seshagiri In-Reply-To: <20260208131355-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SJ0PR13CA0209.namprd13.prod.outlook.com (2603:10b6:a03:2c3::34) To BLAPR15MB3889.namprd15.prod.outlook.com (2603:10b6:208:27a::11) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BLAPR15MB3889:EE_|SN7PR15MB5662:EE_ X-MS-Office365-Filtering-Correlation-Id: cb53532c-154b-49b2-70a1-08de6743c857 X-LD-Processed: 8ae927fe-1255-47a7-a2af-5f3a069daaa2,ExtAddr X-FB-Source: Internal X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|7416014|376014|10070799003|366016; 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Tsirkin wrote: > On Sun, Feb 08, 2026 at 09:54:10AM -0800, Vishwanath Seshagiri 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 >> --- >> 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 >> #include >> #include >> +#include >> >> 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); > > equivalently: > > if (vi->big_packets && !vi->mergeable_rx_bufs) > give_pages(rq, buf); > else > virtnet_put_page(rq, virt_to_head_page(buf), false); > > and then it matches the check we have like in 10 places in > this file. > > maybe it's time for a helper that does vi->big_packets && > !vi->mergeable_rx_bufs? > > maybe virtnet_no_page_pool()? Good idea. I will create the virtnet_no_page_pool() api and use that for making intent clear. > > > > >> } >> >> 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); >> + } >> + > > hmm no this is wrong i think: > > struct virtio_net_hdr_mrg_rxbuf *hdr = buf + header_offset; > int off = buf - page_address(page); > > you should sync from hdr not from buf. > Yeah, the sync offset should be from where device actually writes. I will add change it in v7. > > > besides did not receive_small already sync? > we do not need two syncs. Yes, 2 syncs are redundant. I will keep it in receive_small, so that two syncs do not happen. > > > > >> 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); >> + } > > > similar issue I think. off by header len. ack. will change it in v7. > >> + >> 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); >> + > > nice but where is the sync for reset of buffers? > >> 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); > > ok so we have recycling. > I *think* that since below you set PP_FLAG_DMA_MAP, then page_pool does > not sync_for_device on recycle; > so CPU can write into packet data (e.g. XDP_PASS) and leave dirty cachelines. > After reuse, on non-coherent DMA that can corrupt later packets unless you add > PP_FLAG_DMA_SYNC_DEV (with max_len/offset) or do an explicit > dma_sync_for_device before requeue. > > > See Documentation/core-api/dma-api-howto.rst > > I agree it's annoying since maybe we did not touch it at all. > Right. I initially left it out since dma_sync_for_device is a no-op on coherent platforms where virtio-net is typically deployed, but it's needed for correctness on non-coherent architectures. Will add PP_FLAG_DMA_SYNC_DEV with appropriate max_len/offset in v7. > > > >> 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; >> + } >> + >> + 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 >