On Fri, May 01, 2020 at 01:12:17PM +0300, Denis Kirjanov wrote:
> The patch adds a basic XDP processing to xen-netfront driver.
>
> We ran an XDP program for an RX response received from netback
> driver. Also we request xen-netback to adjust data offset for
> bpf_xdp_adjust_head() header space for custom headers.
>
> synchronization between frontend and backend parts is done
> by using xenbus state switching:
> Reconfiguring -> Reconfigured- > Connected
>
> UDP packets drop rate using xdp program is around 310 kpps
> using ./pktgen_sample04_many_flows.sh and 160 kpps without the patch.
>
> v6:
> - added the missing SOB line
> - fixed subject
>
> v5:
> - split netfront/netback changes
> - added a sync point between backend/frontend on switching to XDP
> - added pagepool API
>
> v4:
> - added verbose patch descriprion
> - don't expose the XDP headroom offset to the domU guest
> - add a modparam to netback to toggle XDP offset
> - don't process jumbo frames for now
>
> v3:
> - added XDP_TX support (tested with xdping echoserver)
> - added XDP_REDIRECT support (tested with modified xdp_redirect_kern)
> - moved xdp negotiation to xen-netback
>
> v2:
> - avoid data copying while passing to XDP
> - tell xen-netback that we need the headroom space
>
> Signed-off-by: Denis Kirjanov <k...@linux-powerpc.org>
> ---
> drivers/net/xen-netfront.c | 302
> ++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 298 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
> index 482c6c8..e7e2c11 100644
> --- a/drivers/net/xen-netfront.c
> +++ b/drivers/net/xen-netfront.c
> @@ -44,6 +44,9 @@
> #include <linux/mm.h>
> #include <linux/slab.h>
> #include <net/ip.h>
> +#include <linux/bpf.h>
> +#include <net/page_pool.h>
> +#include <linux/bpf_trace.h>
>
> #include <xen/xen.h>
> #include <xen/xenbus.h>
> @@ -102,6 +105,8 @@ struct netfront_queue {
> char name[QUEUE_NAME_SIZE]; /* DEVNAME-qN */
> struct netfront_info *info;
>
> + struct bpf_prog __rcu *xdp_prog;
> +
> struct napi_struct napi;
>
> /* Split event channels support, tx_* == rx_* when using
> @@ -144,6 +149,9 @@ struct netfront_queue {
> struct sk_buff *rx_skbs[NET_RX_RING_SIZE];
> grant_ref_t gref_rx_head;
> grant_ref_t grant_rx_ref[NET_RX_RING_SIZE];
> +
> + struct page_pool *page_pool;
> + struct xdp_rxq_info xdp_rxq;
> };
>
> struct netfront_info {
> @@ -159,6 +167,8 @@ struct netfront_info {
> struct netfront_stats __percpu *rx_stats;
> struct netfront_stats __percpu *tx_stats;
>
> + bool netback_has_xdp_headroom;
> +
> atomic_t rx_gso_checksum_fixup;
> };
>
> @@ -167,6 +177,9 @@ struct netfront_rx_info {
> struct xen_netif_extra_info extras[XEN_NETIF_EXTRA_TYPE_MAX - 1];
> };
>
> +static int xennet_xdp_xmit(struct net_device *dev, int n,
> + struct xdp_frame **frames, u32 flags);
> +
> static void skb_entry_set_link(union skb_entry *list, unsigned short id)
> {
> list->link = id;
> @@ -265,8 +278,9 @@ static struct sk_buff *xennet_alloc_one_rx_buffer(struct
> netfront_queue *queue)
> if (unlikely(!skb))
> return NULL;
>
> - page = alloc_page(GFP_ATOMIC | __GFP_NOWARN);
> - if (!page) {
> + page = page_pool_alloc_pages(queue->page_pool,
> + GFP_ATOMIC | __GFP_NOWARN);
You can use page_pool_dev_alloc_pages(), which is called with the exact same
arguments.
> + if (unlikely(!page)) {
> kfree_skb(skb);
> return NULL;
> }
> @@ -778,6 +792,53 @@ static int xennet_get_extras(struct netfront_queue
> *queue,
> return err;
> }
>
> +u32 xennet_run_xdp(struct netfront_queue *queue, struct page *pdata,
> + struct xen_netif_rx_response *rx, struct bpf_prog *prog,
> + struct xdp_buff *xdp)
> +{
> + struct xdp_frame *xdpf;
> + u32 len = rx->status;
> + u32 act = XDP_PASS;
> + int err;
> +
> + xdp->data_hard_start = page_address(pdata);
> + xdp->data = xdp->data_hard_start + XDP_PACKET_HEADROOM;
> + xdp_set_data_meta_invalid(xdp);
> + xdp->data_end = xdp->data + len;
> + xdp->rxq = &queue->xdp_rxq;
> + xdp->handle = 0;
> +
> + act = bpf_prog_run_xdp(prog, xdp);
> + switch (act) {
> + case XDP_TX:
> + get_page(pdata);
> + xdpf = convert_to_xdp_frame(xdp);
> + err = xennet_xdp_xmit(queue->info->netdev, 1, &xdpf, 0);
> + if (unlikely(err < 0))
> + trace_xdp_exception(queue->info->netdev, prog, act);
> + break;
> + case XDP_REDIRECT:
> + get_page(pdata);
> + err = xdp_do_redirect(queue->info->netdev, xdp, prog);
> + if (unlikely(err))
> + trace_xdp_exception(queue->info->netdev, prog, act);
> + xdp_do_flush();
> + break;
> + case XDP_PASS:
> + case XDP_DROP:
> + break;
> +
> + case XDP_ABORTED:
> + trace_xdp_exception(queue->info->netdev, prog, act);
> + break;
> +
> + default:
> + bpf_warn_invalid_xdp_action(act);
> + }
> +
> + return act;
> +}
> +
> static int xennet_get_responses(struct netfront_queue *queue,
> struct netfront_rx_info *rinfo, RING_IDX rp,
> struct sk_buff_head *list)
> @@ -792,6 +853,9 @@ static int xennet_get_responses(struct netfront_queue
> *queue,
> int slots = 1;
> int err = 0;
> unsigned long ret;
> + struct bpf_prog *xdp_prog;
> + struct xdp_buff xdp;
> + u32 verdict;
>
> if (rx->flags & XEN_NETRXF_extra_info) {
> err = xennet_get_extras(queue, extras, rp);
> @@ -827,9 +891,20 @@ static int xennet_get_responses(struct netfront_queue
> *queue,
>
> gnttab_release_grant_reference(&queue->gref_rx_head, ref);
>
> - __skb_queue_tail(list, skb);
> -
> + rcu_read_lock();
> + xdp_prog = rcu_dereference(queue->xdp_prog);
> + if (xdp_prog && !(rx->flags & XEN_NETRXF_more_data)) {
> + /* currently only a single page contains data */
> + WARN_ON_ONCE(skb_shinfo(skb)->nr_frags != 1);
> + verdict = xennet_run_xdp(queue,
> +
> skb_frag_page(&skb_shinfo(skb)->frags[0]),
> + rx, xdp_prog, &xdp);
> + if (verdict != XDP_PASS)
> + err = -EINVAL;
> + }
> + rcu_read_unlock();
> next:
> + __skb_queue_tail(list, skb);
> if (!(rx->flags & XEN_NETRXF_more_data))
> break;
>
> @@ -997,6 +1072,7 @@ static int xennet_poll(struct napi_struct *napi, int
> budget)
> struct sk_buff_head rxq;
> struct sk_buff_head errq;
> struct sk_buff_head tmpq;
> + struct bpf_prog *xdp_prog;
> int err;
>
> spin_lock(&queue->rx_lock);
> @@ -1014,6 +1090,12 @@ static int xennet_poll(struct napi_struct *napi, int
> budget)
> memcpy(rx, RING_GET_RESPONSE(&queue->rx, i), sizeof(*rx));
> memset(extras, 0, sizeof(rinfo.extras));
>
> + rcu_read_lock();
> + xdp_prog = rcu_dereference(queue->xdp_prog);
> + if (xdp_prog)
> + rx->offset = XDP_PACKET_HEADROOM;
> + rcu_read_unlock();
> +
> err = xennet_get_responses(queue, &rinfo, rp, &tmpq);
>
> if (unlikely(err)) {
> @@ -1261,6 +1343,156 @@ static void xennet_poll_controller(struct net_device
> *dev)
> }
> #endif
>
> +#define NETBACK_XDP_HEADROOM_DISABLE 0
> +#define NETBACK_XDP_HEADROOM_ENABLE 1
> +
> +static int talk_to_netback_xdp(struct netfront_info *np, int xdp)
> +{
> + int err;
> +
> + err = xenbus_printf(XBT_NIL, np->xbdev->nodename,
> + "feature-xdp", "%u", xdp);
> + if (err)
> + pr_debug("Error writing feature-xdp\n");
> +
> + return err;
> +}
> +
> +static int xennet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
> + struct netlink_ext_ack *extack)
> +{
> + struct netfront_info *np = netdev_priv(dev);
> + struct bpf_prog *old_prog;
> + unsigned int i, err;
> + unsigned long int max_mtu = XEN_PAGE_SIZE - XDP_PACKET_HEADROOM;
> +
> + if (dev->mtu > max_mtu) {
> + netdev_warn(dev, "XDP requires MTU less than %lu\n", max_mtu);
> + return -EINVAL;
> + }
> +
> + if (!np->netback_has_xdp_headroom)
> + return 0;
> +
> + old_prog = rtnl_dereference(np->queues[0].xdp_prog);
> + if (!old_prog && !prog)
> + return 0;
> +
> + if (prog)
> + bpf_prog_add(prog, dev->real_num_tx_queues);
> +
> + for (i = 0; i < dev->real_num_tx_queues; ++i)
> + rcu_assign_pointer(np->queues[i].xdp_prog, prog);
> +
> + if (old_prog)
> + for (i = 0; i < dev->real_num_tx_queues; ++i)
> + bpf_prog_put(old_prog);
> +
> + xenbus_switch_state(np->xbdev, XenbusStateReconfiguring);
> +
> + err = talk_to_netback_xdp(np, prog ? NETBACK_XDP_HEADROOM_ENABLE:
> + NETBACK_XDP_HEADROOM_DISABLE);
> + if (err)
> + return err;
> +
> + /* avoid race with XDP headroom adjustment */
> + wait_event(module_wq,
> + xenbus_read_driver_state(np->xbdev->otherend) ==
> + XenbusStateReconfigured);
> + xenbus_switch_state(np->xbdev, XenbusStateConnected);
> +
> + return 0;
> +}
> +
> +static u32 xennet_xdp_query(struct net_device *dev)
> +{
> + struct netfront_info *np = netdev_priv(dev);
> + unsigned int num_queues = dev->real_num_tx_queues;
> + unsigned int i;
> + struct netfront_queue *queue;
> + const struct bpf_prog *xdp_prog;
> +
> + for (i = 0; i < num_queues; ++i) {
> + queue = &np->queues[i];
> + xdp_prog = rtnl_dereference(queue->xdp_prog);
> + if (xdp_prog)
> + return xdp_prog->aux->id;
> + }
> +
> + return 0;
> +}
> +
> +static int xennet_xdp(struct net_device *dev, struct netdev_bpf *xdp)
> +{
> + switch (xdp->command) {
> + case XDP_SETUP_PROG:
> + return xennet_xdp_set(dev, xdp->prog, xdp->extack);
> + case XDP_QUERY_PROG:
> + xdp->prog_id = xennet_xdp_query(dev);
> + return 0;
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +static int xennet_xdp_xmit_one(struct net_device *dev, struct xdp_frame
> *xdpf)
> +{
> + struct netfront_info *np = netdev_priv(dev);
> + struct netfront_stats *tx_stats = this_cpu_ptr(np->tx_stats);
> + struct netfront_queue *queue = NULL;
> + unsigned int num_queues = dev->real_num_tx_queues;
> + unsigned long flags;
> + int notify;
> + struct xen_netif_tx_request *tx;
> +
> + queue = &np->queues[smp_processor_id() % num_queues];
> +
> + spin_lock_irqsave(&queue->tx_lock, flags);
> +
> + tx = xennet_make_first_txreq(queue, NULL,
> + virt_to_page(xdpf->data),
> + offset_in_page(xdpf->data),
> + xdpf->len);
> +
> + RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&queue->tx, notify);
> + if (notify)
> + notify_remote_via_irq(queue->tx_irq);
> +
> + u64_stats_update_begin(&tx_stats->syncp);
> + tx_stats->bytes += xdpf->len;
> + tx_stats->packets++;
> + u64_stats_update_end(&tx_stats->syncp);
> +
> + xennet_tx_buf_gc(queue);
> +
> + spin_unlock_irqrestore(&queue->tx_lock, flags);
> + return 0;
> +}
> +
> +static int xennet_xdp_xmit(struct net_device *dev, int n,
> + struct xdp_frame **frames, u32 flags)
> +{
> + int drops = 0;
> + int i, err;
> +
> + if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
> + return -EINVAL;
> +
> + for (i = 0; i < n; i++) {
> + struct xdp_frame *xdpf = frames[i];
> +
> + if (!xdpf)
> + continue;
> + err = xennet_xdp_xmit_one(dev, xdpf);
> + if (err) {
> + xdp_return_frame_rx_napi(xdpf);
> + drops++;
> + }
> + }
> +
> + return n - drops;
> +}
> +
> static const struct net_device_ops xennet_netdev_ops = {
> .ndo_open = xennet_open,
> .ndo_stop = xennet_close,
> @@ -1272,6 +1504,8 @@ static void xennet_poll_controller(struct net_device
> *dev)
> .ndo_fix_features = xennet_fix_features,
> .ndo_set_features = xennet_set_features,
> .ndo_select_queue = xennet_select_queue,
> + .ndo_bpf = xennet_xdp,
> + .ndo_xdp_xmit = xennet_xdp_xmit,
> #ifdef CONFIG_NET_POLL_CONTROLLER
> .ndo_poll_controller = xennet_poll_controller,
> #endif
> @@ -1419,6 +1653,8 @@ static void xennet_disconnect_backend(struct
> netfront_info *info)
> queue->rx_ring_ref = GRANT_INVALID_REF;
> queue->tx.sring = NULL;
> queue->rx.sring = NULL;
> +
> + page_pool_destroy(queue->page_pool);
> }
> }
>
> @@ -1754,6 +1990,51 @@ static void xennet_destroy_queues(struct netfront_info
> *info)
> info->queues = NULL;
> }
>
> +
> +
> +static int xennet_create_page_pool(struct netfront_queue *queue)
> +{
> + int err;
> + struct page_pool_params pp_params = {
> + .order = 0,
> + .flags = 0,
> + .pool_size = NET_RX_RING_SIZE,
> + .nid = NUMA_NO_NODE,
> + .dev = &queue->info->netdev->dev,
> + .offset = XDP_PACKET_HEADROOM,
> + .max_len = XEN_PAGE_SIZE - XDP_PACKET_HEADROOM,
> + };
> +
> + queue->page_pool = page_pool_create(&pp_params);
> + if (IS_ERR(queue->page_pool)) {
> + err = PTR_ERR(queue->page_pool);
> + queue->page_pool = NULL;
> + return err;
> + }
> +
> + err = xdp_rxq_info_reg(&queue->xdp_rxq, queue->info->netdev,
> + queue->id);
> + if (err) {
> + netdev_err(queue->info->netdev, "xdp_rxq_info_reg failed\n");
> + goto err_free_pp;
> + }
> +
> + err = xdp_rxq_info_reg_mem_model(&queue->xdp_rxq,
> + MEM_TYPE_PAGE_ORDER0, NULL);
> + if (err) {
> + netdev_err(queue->info->netdev, "xdp_rxq_info_reg_mem_model
> failed\n");
> + goto err_unregister_rxq;
> + }
> + return 0;
> +
> +err_unregister_rxq:
> + xdp_rxq_info_unreg(&queue->xdp_rxq);
> +err_free_pp:
> + page_pool_destroy(queue->page_pool);
> + queue->page_pool = NULL;
> + return err;
> +}
> +
> static int xennet_create_queues(struct netfront_info *info,
> unsigned int *num_queues)
> {
> @@ -1779,6 +2060,14 @@ static int xennet_create_queues(struct netfront_info
> *info,
> break;
> }
>
> + /* use page pool recycling instead of buddy allocator */
> + ret = xennet_create_page_pool(queue);
> + if (ret < 0) {
> + dev_err(&info->xbdev->dev, "can't allocate page
> pool\n");
> + *num_queues = i;
> + return ret;
> + }
> +
> netif_napi_add(queue->info->netdev, &queue->napi,
> xennet_poll, 64);
> if (netif_running(info->netdev))
> @@ -1825,6 +2114,8 @@ static int talk_to_netback(struct xenbus_device *dev,
> goto out_unlocked;
> }
>
> + info->netback_has_xdp_headroom =
> xenbus_read_unsigned(info->xbdev->otherend,
> +
> "feature-xdp-headroom", 0);
> rtnl_lock();
> if (info->queues)
> xennet_destroy_queues(info);
> @@ -1959,6 +2250,8 @@ static int xennet_connect(struct net_device *dev)
> err = talk_to_netback(np->xbdev, np);
> if (err)
> return err;
> + if (np->netback_has_xdp_headroom)
> + pr_info("backend supports XDP headroom\n");
>
> /* talk_to_netback() sets the correct number of queues */
> num_queues = dev->real_num_tx_queues;
> @@ -2020,6 +2313,7 @@ static void netback_changed(struct xenbus_device *dev,
> case XenbusStateInitialised:
> case XenbusStateReconfiguring:
> case XenbusStateReconfigured:
> + break;
> case XenbusStateUnknown:
> break;
>
> --
> 1.8.3.1
>
