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Date: Thu, 5 Mar 2020 16:23:31 +0300
From: Denis Kirjanov <kirjanov@...il.com>
To: Ilias Apalodimas <ilias.apalodimas@...aro.org>
Cc: Denis Kirjanov <kda@...ux-powerpc.org>, netdev@...r.kernel.org,
jgross@...e.com
Subject: Re: [PATCH net-next v2] xen-netfront: add basic XDP support
On 3/5/20, Ilias Apalodimas <ilias.apalodimas@...aro.org> wrote:
> Hi Denis,
>
> There's a bunch of things still missing from my remarks on V1.
> XDP is not supposed to allocate and free pages constantly as that's one of
> the
> things that's making it fast.
Hi Ilias,
I've removed the copying to an allocated page so there is no page
allocation/free logic added.
>
> You are also missing proper support for XDP_REDIRECT, ndo_xdp_xmit. We
> usually
> require the whole functionality to merge the driver.
I wanted to minimize changes and send follow-up patches
>
>
> On Mon, Mar 02, 2020 at 05:21:14PM +0300, Denis Kirjanov wrote:
>>
> [...]
>> +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)
>> +{
>> + u32 len = rx->status;
>> + u32 act = XDP_PASS;
>> +
>> + 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->handle = 0;
>> +
>> + act = bpf_prog_run_xdp(prog, xdp);
>> + switch (act) {
>> + case XDP_PASS:
>> + case XDP_TX:
>> + case XDP_DROP:
>
> Maybe i am missing something on the usage, but XDP_TX and XDROP are handled
> similarly?
> XDP_TX is supposed to sent the packet out of the interface it arrived.
Yep, you're right. I'll add it to the next version.
Thanks!
>
>> + break;
>> +
>> + case XDP_ABORTED:
>> + trace_xdp_exception(queue->info->netdev, prog, act);
>> + break;
>> +
>> + default:
>> + bpf_warn_invalid_xdp_action(act);
>> + }
>> +
>> + if (act != XDP_PASS && act != XDP_TX)
>> + xdp->data_hard_start = NULL;
>> +
>> + 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 +830,9 @@ 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);
>> @@ -827,6 +868,22 @@ static int xennet_get_responses(struct netfront_queue
>> *queue,
>>
>> gnttab_release_grant_reference(&queue->gref_rx_head, ref);
>>
>> + rcu_read_lock();
>> + xdp_prog = rcu_dereference(queue->xdp_prog);
>> + if (xdp_prog) {
>> + /* 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 && verdict != XDP_TX) {
>> + err = -EINVAL;
>> + goto next;
>> + }
>> +
>> + }
>> + rcu_read_unlock();
>> __skb_queue_tail(list, skb);
>>
>> next:
>> @@ -1261,6 +1318,105 @@ 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)
>> +{
>> + struct xenbus_transaction xbt;
>> + const char *message;
>> + int err;
>> +
>> +again:
>> + err = xenbus_transaction_start(&xbt);
>> + if (err) {
>> + xenbus_dev_fatal(np->xbdev, err, "starting transaction");
>> + goto out;
>> + }
>> +
>> + err = xenbus_printf(xbt, np->xbdev->nodename, "feature-xdp", "%d",
>> xdp);
>> + if (err) {
>> + message = "writing feature-xdp";
>> + goto abort_transaction;
>> + }
>> +
>> + err = xenbus_transaction_end(xbt, 0);
>> + if (err) {
>> + if (err == -EAGAIN)
>> + goto again;
>> + }
>> +
>> + return 0;
>> +
>> +abort_transaction:
>> + xenbus_dev_fatal(np->xbdev, err, "%s", message);
>> + xenbus_transaction_end(xbt, 1);
>> +out:
>> + 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;
>> +
>> + 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);
>> +
>> + err = talk_to_netback_xdp(np, old_prog ? NETBACK_XDP_HEADROOM_DISABLE:
>> + NETBACK_XDP_HEADROOM_ENABLE);
>> + if (err)
>> + return err;
>> +
>> + xenbus_switch_state(np->xbdev, XenbusStateReconfiguring);
>> +
>> + 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 const struct net_device_ops xennet_netdev_ops = {
>> .ndo_open = xennet_open,
>> .ndo_stop = xennet_close,
>> @@ -1272,6 +1428,7 @@ 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,
>> #ifdef CONFIG_NET_POLL_CONTROLLER
>> .ndo_poll_controller = xennet_poll_controller,
>> #endif
>> --
>> 1.8.3.1
>>
> Cheers
> /Ilias
>
--
Regards / Mit besten Grüßen,
Denis
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