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Date: Mon, 22 Jun 2020 11:10:10 +0100
From: Paul Durrant <xadimgnik@...il.com>
To: "'Denis Kirjanov'" <kda@...ux-powerpc.org>,
<netdev@...r.kernel.org>
Cc: <brouer@...hat.com>, <jgross@...e.com>, <wei.liu@...nel.org>,
<ilias.apalodimas@...aro.org>
Subject: RE: [PATCH net-next v10 3/3] xen networking: add XDP offset adjustment to xen-netback
> -----Original Message-----
> From: Denis Kirjanov <kda@...ux-powerpc.org>
> Sent: 22 June 2020 10:21
> To: netdev@...r.kernel.org
> Cc: brouer@...hat.com; jgross@...e.com; wei.liu@...nel.org; paul@....org; ilias.apalodimas@...aro.org
> Subject: [PATCH net-next v10 3/3] xen networking: add XDP offset adjustment to xen-netback
>
> the patch basically adds the offset adjustment and netfront
> state reading to make XDP work on netfront side.
>
> Signed-off-by: Denis Kirjanov <kda@...ux-powerpc.org>
> ---
> drivers/net/xen-netback/common.h | 4 ++++
> drivers/net/xen-netback/interface.c | 2 ++
> drivers/net/xen-netback/netback.c | 7 +++++++
> drivers/net/xen-netback/rx.c | 15 ++++++++++++++-
> drivers/net/xen-netback/xenbus.c | 32 ++++++++++++++++++++++++++++++++
> 5 files changed, 59 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
> index 05847eb..f14dc10 100644
> --- a/drivers/net/xen-netback/common.h
> +++ b/drivers/net/xen-netback/common.h
> @@ -281,6 +281,9 @@ struct xenvif {
> u8 ipv6_csum:1;
> u8 multicast_control:1;
>
> + /* headroom requested by xen-netfront */
> + u16 netfront_xdp_headroom;
> +
> /* Is this interface disabled? True when backend discovers
> * frontend is rogue.
> */
> @@ -395,6 +398,7 @@ static inline pending_ring_idx_t nr_pending_reqs(struct xenvif_queue *queue)
> irqreturn_t xenvif_interrupt(int irq, void *dev_id);
>
> extern bool separate_tx_rx_irq;
> +extern bool provides_xdp_headroom;
>
> extern unsigned int rx_drain_timeout_msecs;
> extern unsigned int rx_stall_timeout_msecs;
> diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
> index 0c8a02a..fc16edd 100644
> --- a/drivers/net/xen-netback/interface.c
> +++ b/drivers/net/xen-netback/interface.c
> @@ -483,6 +483,8 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
> vif->queues = NULL;
> vif->num_queues = 0;
>
> + vif->netfront_xdp_headroom = 0;
> +
How about just 'xdp_headroom'? It's shorter to type :-)
> spin_lock_init(&vif->lock);
> INIT_LIST_HEAD(&vif->fe_mcast_addr);
>
> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
> index 315dfc6..6dfca72 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -96,6 +96,13 @@
> module_param_named(hash_cache_size, xenvif_hash_cache_size, uint, 0644);
> MODULE_PARM_DESC(hash_cache_size, "Number of flows in the hash cache");
>
> +/* The module parameter tells that we have to put data
> + * for xen-netfront with the XDP_PACKET_HEADROOM offset
> + * needed for XDP processing
> + */
> +bool provides_xdp_headroom = true;
> +module_param(provides_xdp_headroom, bool, 0644);
> +
> static void xenvif_idx_release(struct xenvif_queue *queue, u16 pending_idx,
> u8 status);
>
> diff --git a/drivers/net/xen-netback/rx.c b/drivers/net/xen-netback/rx.c
> index ef58870..c5e9e14 100644
> --- a/drivers/net/xen-netback/rx.c
> +++ b/drivers/net/xen-netback/rx.c
> @@ -258,6 +258,19 @@ static void xenvif_rx_next_skb(struct xenvif_queue *queue,
> pkt->extra_count++;
> }
>
> + if (queue->vif->netfront_xdp_headroom) {
> + struct xen_netif_extra_info *extra;
> +
> + extra = &pkt->extras[XEN_NETIF_EXTRA_TYPE_XDP - 1];
> +
> + memset(extra, 0, sizeof(struct xen_netif_extra_info));
> + extra->u.xdp.headroom = queue->vif->netfront_xdp_headroom;
> + extra->type = XEN_NETIF_EXTRA_TYPE_XDP;
> + extra->flags = 0;
> +
> + pkt->extra_count++;
> + }
> +
> if (skb->sw_hash) {
> struct xen_netif_extra_info *extra;
>
> @@ -356,7 +369,7 @@ static void xenvif_rx_data_slot(struct xenvif_queue *queue,
> struct xen_netif_rx_request *req,
> struct xen_netif_rx_response *rsp)
> {
> - unsigned int offset = 0;
> + unsigned int offset = queue->vif->netfront_xdp_headroom;
> unsigned int flags;
>
> do {
> diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
> index 286054b..c67abc5 100644
> --- a/drivers/net/xen-netback/xenbus.c
> +++ b/drivers/net/xen-netback/xenbus.c
> @@ -393,6 +393,22 @@ static void set_backend_state(struct backend_info *be,
> }
> }
>
> +static void read_xenbus_frontend_xdp(struct backend_info *be,
> + struct xenbus_device *dev)
> +{
> + struct xenvif *vif = be->vif;
> + u16 headroom;
> + int err;
> +
> + err = xenbus_scanf(XBT_NIL, dev->otherend,
> + "netfront-xdp-headroom", "%hu", &headroom);
Isn't it just "xdp-headroom"? That's what the comments in netif.h state.
> + if (err < 0) {
> + vif->netfront_xdp_headroom = 0;
> + return;
> + }
What is a reasonable value for maximum headroom? Do we really want to allow values all the way up to 65535?
Paul
> + vif->netfront_xdp_headroom = headroom;
> +}
> +
> /**
> * Callback received when the frontend's state changes.
> */
> @@ -417,6 +433,11 @@ static void frontend_changed(struct xenbus_device *dev,
> set_backend_state(be, XenbusStateConnected);
> break;
>
> + case XenbusStateReconfiguring:
> + read_xenbus_frontend_xdp(be, dev);
> + xenbus_switch_state(dev, XenbusStateReconfigured);
> + break;
> +
> case XenbusStateClosing:
> set_backend_state(be, XenbusStateClosing);
> break;
> @@ -947,6 +968,8 @@ static int read_xenbus_vif_flags(struct backend_info *be)
> vif->ipv6_csum = !!xenbus_read_unsigned(dev->otherend,
> "feature-ipv6-csum-offload", 0);
>
> + read_xenbus_frontend_xdp(be, dev);
> +
> return 0;
> }
>
> @@ -1036,6 +1059,15 @@ static int netback_probe(struct xenbus_device *dev,
> goto abort_transaction;
> }
>
> + /* we can adjust a headroom for netfront XDP processing */
> + err = xenbus_printf(xbt, dev->nodename,
> + "feature-xdp-headroom", "%d",
> + provides_xdp_headroom);
> + if (err) {
> + message = "writing feature-xdp-headroom";
> + goto abort_transaction;
> + }
> +
> /* We don't support rx-flip path (except old guests who
> * don't grok this feature flag).
> */
> --
> 1.8.3.1
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