> -----Original Message-----
> From: Denis Kirjanov <k...@linux-powerpc.org>
> Sent: 11 May 2020 11:22
> To: netdev@vger.kernel.org
> Cc: bro...@redhat.com; jgr...@suse.com; wei....@kernel.org; p...@xen.org;
> ilias.apalodi...@linaro.org
> Subject: [PATCH net-next v9 2/2] 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 <denis.kirja...@suse.com>
> ---
> drivers/net/xen-netback/common.h | 2 ++
> drivers/net/xen-netback/netback.c | 7 +++++++
> drivers/net/xen-netback/rx.c | 7 ++++++-
> drivers/net/xen-netback/xenbus.c | 28 ++++++++++++++++++++++++++++
> 4 files changed, 43 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/xen-netback/common.h
> b/drivers/net/xen-netback/common.h
> index 05847eb..4a148d6 100644
> --- a/drivers/net/xen-netback/common.h
> +++ b/drivers/net/xen-netback/common.h
> @@ -280,6 +280,7 @@ struct xenvif {
> u8 ip_csum:1;
> u8 ipv6_csum:1;
> u8 multicast_control:1;
> + u8 xdp_enabled:1;
>
> /* Is this interface disabled? True when backend discovers
> * frontend is rogue.
> @@ -395,6 +396,7 @@ 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/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..c97c98e 100644
> --- a/drivers/net/xen-netback/rx.c
> +++ b/drivers/net/xen-netback/rx.c
> @@ -33,6 +33,11 @@
> #include <xen/xen.h>
> #include <xen/events.h>
>
> +static int xenvif_rx_xdp_offset(struct xenvif *vif)
> +{
> + return vif->xdp_enabled ? XDP_PACKET_HEADROOM : 0;
> +}
> +
> static bool xenvif_rx_ring_slots_available(struct xenvif_queue *queue)
> {
> RING_IDX prod, cons;
> @@ -356,7 +361,7 @@ 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 = xenvif_rx_xdp_offset(queue->vif);
> unsigned int flags;
>
> do {
> diff --git a/drivers/net/xen-netback/xenbus.c
> b/drivers/net/xen-netback/xenbus.c
> index 286054b..d447191 100644
> --- a/drivers/net/xen-netback/xenbus.c
> +++ b/drivers/net/xen-netback/xenbus.c
> @@ -393,6 +393,20 @@ 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;
> + unsigned int val;
> + int err;
> +
> + err = xenbus_scanf(XBT_NIL, dev->otherend,
> + "feature-xdp", "%u", &val);
> + if (err != 1)
> + return;
> + vif->xdp_enabled = val;
> +}
> +
> /**
> * Callback received when the frontend's state changes.
> */
> @@ -417,6 +431,11 @@ static void frontend_changed(struct xenbus_device *dev,
> set_backend_state(be, XenbusStateConnected);
> break;
>
> + case XenbusStateReconfiguring:
> + read_xenbus_frontend_xdp(be, dev);
I think this being the only call to read_xenbus_frontend_xdp() is still a
problem. What happens if netback is reloaded against a
netfront that has already enabled 'feature-xdp'? AFAICT vif->xdp_enabled would
remain false after the reload.
Paul
> + xenbus_switch_state(dev, XenbusStateReconfigured);
> + break;
> +
> case XenbusStateClosing:
> set_backend_state(be, XenbusStateClosing);
> break;
> @@ -1036,6 +1055,15 @@ 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
