ice: introduce XDP_TX fallback path

Under rare circumstances there might be a situation where a requirement
of having XDP Tx queue per CPU could not be fulfilled and some of the Tx
resources have to be shared between CPUs. This yields a need for placing
accesses to xdp_ring inside a critical section protected by spinlock.
These accesses happen to be in the hot path, so let's introduce the
static branch that will be triggered from the control plane when driver
could not provide Tx queue dedicated for XDP on each CPU.

Currently, the design that has been picked is to allow any number of XDP
Tx queues that is at least half of a count of CPUs that platform has.
For lower number driver will bail out with a response to user that there
were not enough Tx resources that would allow configuring XDP. The
sharing of rings is signalled via static branch enablement which in turn
indicates that lock for xdp_ring accesses needs to be taken in hot path.

Approach based on static branch has no impact on performance of a
non-fallback path. One thing that is needed to be mentioned is a fact
that the static branch will act as a global driver switch, meaning that
if one PF got out of Tx resources, then other PFs that ice driver is
servicing will suffer. However, given the fact that HW that ice driver
is handling has 1024 Tx queues per each PF, this is currently an
unlikely scenario.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: George Kuruvinakunnel <george.kuruvinakunnel@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

diff --git a/drivers/net/ethernet/intel/ice/ice.h b/drivers/net/ethernet/intel/ice/ice.h
index 35cf1865beb4386ad22237563e6e77fa6674919f..aeac6cd0e74f72c01e35586d0dba8383993c4edb 100644 (file)
--- a/drivers/net/ethernet/intel/ice/ice.h
+++ b/drivers/net/ethernet/intel/ice/ice.h
@@ -167,6 +167,8 @@ enum ice_feature {
        ICE_F_MAX
 };
 
+DECLARE_STATIC_KEY_FALSE(ice_xdp_locking_key);
+
 struct ice_txq_meta {
        u32 q_teid;     /* Tx-scheduler element identifier */
        u16 q_id;       /* Entry in VSI's txq_map bitmap */
@@ -716,6 +718,7 @@ int ice_up(struct ice_vsi *vsi);
 int ice_down(struct ice_vsi *vsi);
 int ice_vsi_cfg(struct ice_vsi *vsi);
 struct ice_vsi *ice_lb_vsi_setup(struct ice_pf *pf, struct ice_port_info *pi);
+int ice_vsi_determine_xdp_res(struct ice_vsi *vsi);
 int ice_prepare_xdp_rings(struct ice_vsi *vsi, struct bpf_prog *prog);
 int ice_destroy_xdp_rings(struct ice_vsi *vsi);
 int

diff --git a/drivers/net/ethernet/intel/ice/ice_lib.c b/drivers/net/ethernet/intel/ice/ice_lib.c
index 58fad5f820769e1d43c23e279b8a877be818987f..e4dc4435c8f541551883382b2eac6005f7038f15 100644 (file)
--- a/drivers/net/ethernet/intel/ice/ice_lib.c
+++ b/drivers/net/ethernet/intel/ice/ice_lib.c
@@ -3215,7 +3215,9 @@ int ice_vsi_rebuild(struct ice_vsi *vsi, bool init_vsi)
 
                ice_vsi_map_rings_to_vectors(vsi);
                if (ice_is_xdp_ena_vsi(vsi)) {
-                       vsi->num_xdp_txq = num_possible_cpus();
+                       ret = ice_vsi_determine_xdp_res(vsi);
+                       if (ret)
+                               goto err_vectors;
                        ret = ice_prepare_xdp_rings(vsi, vsi->xdp_prog);
                        if (ret)
                                goto err_vectors;

diff --git a/drivers/net/ethernet/intel/ice/ice_main.c b/drivers/net/ethernet/intel/ice/ice_main.c
index 214eebb7bbd8d0ca7efedd09cfc7ce1b82d2a915..ccd9b9514001566323bee8447f9a95a16524f557 100644 (file)
--- a/drivers/net/ethernet/intel/ice/ice_main.c
+++ b/drivers/net/ethernet/intel/ice/ice_main.c
@@ -44,6 +44,8 @@ MODULE_PARM_DESC(debug, "netif level (0=none,...,16=all)");
 #endif /* !CONFIG_DYNAMIC_DEBUG */
 
 static DEFINE_IDA(ice_aux_ida);
+DEFINE_STATIC_KEY_FALSE(ice_xdp_locking_key);
+EXPORT_SYMBOL(ice_xdp_locking_key);
 
 static struct workqueue_struct *ice_wq;
 static const struct net_device_ops ice_netdev_safe_mode_ops;
@@ -2397,14 +2399,19 @@ static int ice_xdp_alloc_setup_rings(struct ice_vsi *vsi)
                        goto free_xdp_rings;
                ice_set_ring_xdp(xdp_ring);
                xdp_ring->xsk_pool = ice_tx_xsk_pool(xdp_ring);
+               spin_lock_init(&xdp_ring->tx_lock);
                for (j = 0; j < xdp_ring->count; j++) {
                        tx_desc = ICE_TX_DESC(xdp_ring, j);
                        tx_desc->cmd_type_offset_bsz = cpu_to_le64(ICE_TX_DESC_DTYPE_DESC_DONE);
                }
        }
 
-       ice_for_each_rxq(vsi, i)
-               vsi->rx_rings[i]->xdp_ring = vsi->xdp_rings[i];
+       ice_for_each_rxq(vsi, i) {
+               if (static_key_enabled(&ice_xdp_locking_key))
+                       vsi->rx_rings[i]->xdp_ring = vsi->xdp_rings[i % vsi->num_xdp_txq];
+               else
+                       vsi->rx_rings[i]->xdp_ring = vsi->xdp_rings[i];
+       }
 
        return 0;
 
@@ -2469,6 +2476,10 @@ int ice_prepare_xdp_rings(struct ice_vsi *vsi, struct bpf_prog *prog)
        if (__ice_vsi_get_qs(&xdp_qs_cfg))
                goto err_map_xdp;
 
+       if (static_key_enabled(&ice_xdp_locking_key))
+               netdev_warn(vsi->netdev,
+                           "Could not allocate one XDP Tx ring per CPU, XDP_TX/XDP_REDIRECT actions will be slower\n");
+
        if (ice_xdp_alloc_setup_rings(vsi))
                goto clear_xdp_rings;
 
@@ -2585,6 +2596,9 @@ free_qmap:
        devm_kfree(ice_pf_to_dev(pf), vsi->xdp_rings);
        vsi->xdp_rings = NULL;
 
+       if (static_key_enabled(&ice_xdp_locking_key))
+               static_branch_dec(&ice_xdp_locking_key);
+
        if (ice_is_reset_in_progress(pf->state) || !vsi->q_vectors[0])
                return 0;
 
@@ -2619,6 +2633,29 @@ static void ice_vsi_rx_napi_schedule(struct ice_vsi *vsi)
        }
 }
 
+/**
+ * ice_vsi_determine_xdp_res - figure out how many Tx qs can XDP have
+ * @vsi: VSI to determine the count of XDP Tx qs
+ *
+ * returns 0 if Tx qs count is higher than at least half of CPU count,
+ * -ENOMEM otherwise
+ */
+int ice_vsi_determine_xdp_res(struct ice_vsi *vsi)
+{
+       u16 avail = ice_get_avail_txq_count(vsi->back);
+       u16 cpus = num_possible_cpus();
+
+       if (avail < cpus / 2)
+               return -ENOMEM;
+
+       vsi->num_xdp_txq = min_t(u16, avail, cpus);
+
+       if (vsi->num_xdp_txq < cpus)
+               static_branch_inc(&ice_xdp_locking_key);
+
+       return 0;
+}
+
 /**
  * ice_xdp_setup_prog - Add or remove XDP eBPF program
  * @vsi: VSI to setup XDP for
@@ -2648,10 +2685,14 @@ ice_xdp_setup_prog(struct ice_vsi *vsi, struct bpf_prog *prog,
        }
 
        if (!ice_is_xdp_ena_vsi(vsi) && prog) {
-               vsi->num_xdp_txq = num_possible_cpus();
-               xdp_ring_err = ice_prepare_xdp_rings(vsi, prog);
-               if (xdp_ring_err)
-                       NL_SET_ERR_MSG_MOD(extack, "Setting up XDP Tx resources failed");
+               xdp_ring_err = ice_vsi_determine_xdp_res(vsi);
+               if (xdp_ring_err) {
+                       NL_SET_ERR_MSG_MOD(extack, "Not enough Tx resources for XDP");
+               } else {
+                       xdp_ring_err = ice_prepare_xdp_rings(vsi, prog);
+                       if (xdp_ring_err)
+                               NL_SET_ERR_MSG_MOD(extack, "Setting up XDP Tx resources failed");
+               }
        } else if (ice_is_xdp_ena_vsi(vsi) && !prog) {
                xdp_ring_err = ice_destroy_xdp_rings(vsi);
                if (xdp_ring_err)

diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.c b/drivers/net/ethernet/intel/ice/ice_txrx.c
index 927517e18ce30fe0e7d1de28a4e112c56d0db33e..01ae331927bd0d51a5bf1d35a2bec36e59eff808 100644 (file)
--- a/drivers/net/ethernet/intel/ice/ice_txrx.c
+++ b/drivers/net/ethernet/intel/ice/ice_txrx.c
@@ -547,7 +547,11 @@ ice_run_xdp(struct ice_rx_ring *rx_ring, struct xdp_buff *xdp,
        case XDP_PASS:
                return ICE_XDP_PASS;
        case XDP_TX:
+               if (static_branch_unlikely(&ice_xdp_locking_key))
+                       spin_lock(&xdp_ring->tx_lock);
                err = ice_xmit_xdp_ring(xdp->data, xdp->data_end - xdp->data, xdp_ring);
+               if (static_branch_unlikely(&ice_xdp_locking_key))
+                       spin_unlock(&xdp_ring->tx_lock);
                if (err == ICE_XDP_CONSUMED)
                        goto out_failure;
                return err;
@@ -599,7 +603,14 @@ ice_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames,
        if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
                return -EINVAL;
 
-       xdp_ring = vsi->xdp_rings[queue_index];
+       if (static_branch_unlikely(&ice_xdp_locking_key)) {
+               queue_index %= vsi->num_xdp_txq;
+               xdp_ring = vsi->xdp_rings[queue_index];
+               spin_lock(&xdp_ring->tx_lock);
+       } else {
+               xdp_ring = vsi->xdp_rings[queue_index];
+       }
+
        for (i = 0; i < n; i++) {
                struct xdp_frame *xdpf = frames[i];
                int err;
@@ -613,6 +624,9 @@ ice_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames,
        if (unlikely(flags & XDP_XMIT_FLUSH))
                ice_xdp_ring_update_tail(xdp_ring);
 
+       if (static_branch_unlikely(&ice_xdp_locking_key))
+               spin_unlock(&xdp_ring->tx_lock);
+
        return nxmit;
 }
 

diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.h b/drivers/net/ethernet/intel/ice/ice_txrx.h
index 22de016adbcad1cb7614919ff9427f8c2ccf9b9c..c759a02bfce4c029124ae4d7d4ab2ff16bbc6cd3 100644 (file)
--- a/drivers/net/ethernet/intel/ice/ice_txrx.h
+++ b/drivers/net/ethernet/intel/ice/ice_txrx.h
@@ -329,6 +329,7 @@ struct ice_tx_ring {
        struct rcu_head rcu;            /* to avoid race on free */
        DECLARE_BITMAP(xps_state, ICE_TX_NBITS);        /* XPS Config State */
        struct ice_ptp_tx *tx_tstamps;
+       spinlock_t tx_lock;
        u32 txq_teid;                   /* Added Tx queue TEID */
 #define ICE_TX_FLAGS_RING_XDP          BIT(0)
        u8 flags;

diff --git a/drivers/net/ethernet/intel/ice/ice_txrx_lib.c b/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
index d55db9cedc9b330b78eddaa4b27115946fa6d420..1dd7e84f41f8777c2e9804ab96897fc76806760b 100644 (file)
--- a/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
+++ b/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
@@ -350,6 +350,11 @@ void ice_finalize_xdp_rx(struct ice_tx_ring *xdp_ring, unsigned int xdp_res)
        if (xdp_res & ICE_XDP_REDIR)
                xdp_do_flush_map();
 
-       if (xdp_res & ICE_XDP_TX)
+       if (xdp_res & ICE_XDP_TX) {
+               if (static_branch_unlikely(&ice_xdp_locking_key))
+                       spin_lock(&xdp_ring->tx_lock);
                ice_xdp_ring_update_tail(xdp_ring);
+               if (static_branch_unlikely(&ice_xdp_locking_key))
+                       spin_unlock(&xdp_ring->tx_lock);
+       }
 }