[PATCH net-next 11/16] libeth: xdp: add RSS hash hint and XDP features setup helpers

[Tony Nguyen <anthony.l.nguyen@intel.com>]

From: Alexander Lobakin <aleksander.lobakin@intel.com>

End the XDP section by adding helpers to setup XDP features, flipping
.ndo_xdp_xmit() support at runtime (in case when it's not always on),
and calculating the queue clean/refill threshold.

Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
---
 drivers/net/ethernet/intel/libeth/xdp.c | 69 +++++++++++++++++++
 include/net/libeth/xdp.h                | 90 +++++++++++++++++++++++++
 2 files changed, 159 insertions(+)

diff --git a/drivers/net/ethernet/intel/libeth/xdp.c b/drivers/net/ethernet/intel/libeth/xdp.c
index a20ba2478097..975c34af2f0f 100644
--- a/drivers/net/ethernet/intel/libeth/xdp.c
+++ b/drivers/net/ethernet/intel/libeth/xdp.c
@@ -338,6 +338,75 @@ void libeth_xdp_return_buff_bulk(const struct skb_shared_info *sinfo,
 }
 EXPORT_SYMBOL_GPL(libeth_xdp_return_buff_bulk);
 
+/* Misc */
+
+/**
+ * libeth_xdp_queue_threshold - calculate XDP queue clean/refill threshold
+ * @count: number of descriptors in the queue
+ *
+ * The threshold is the limit at which RQs start to refill (when the number of
+ * empty buffers exceeds it) and SQs get cleaned up (when the number of free
+ * descriptors goes below it). To speed up hotpath processing, threshold is
+ * always pow-2, closest to 1/4 of the queue length.
+ * Don't call it on hotpath, calculate and cache the threshold during the
+ * queue initialization.
+ *
+ * Return: the calculated threshold.
+ */
+u32 libeth_xdp_queue_threshold(u32 count)
+{
+	u32 quarter, low, high;
+
+	if (likely(is_power_of_2(count)))
+		return count >> 2;
+
+	quarter = DIV_ROUND_CLOSEST(count, 4);
+	low = rounddown_pow_of_two(quarter);
+	high = roundup_pow_of_two(quarter);
+
+	return high - quarter <= quarter - low ? high : low;
+}
+EXPORT_SYMBOL_GPL(libeth_xdp_queue_threshold);
+
+/**
+ * __libeth_xdp_set_features - set XDP features for netdev
+ * @dev: &net_device to configure
+ * @xmo: XDP metadata ops (Rx hints)
+ *
+ * Set all the features libeth_xdp supports. Only the first argument is
+ * necessary.
+ * Use the non-underscored versions in drivers instead.
+ */
+void __libeth_xdp_set_features(struct net_device *dev,
+			       const struct xdp_metadata_ops *xmo)
+{
+	xdp_set_features_flag(dev,
+			      NETDEV_XDP_ACT_BASIC |
+			      NETDEV_XDP_ACT_REDIRECT |
+			      NETDEV_XDP_ACT_NDO_XMIT |
+			      NETDEV_XDP_ACT_RX_SG |
+			      NETDEV_XDP_ACT_NDO_XMIT_SG);
+	dev->xdp_metadata_ops = xmo;
+}
+EXPORT_SYMBOL_GPL(__libeth_xdp_set_features);
+
+/**
+ * libeth_xdp_set_redirect - toggle the XDP redirect feature
+ * @dev: &net_device to configure
+ * @enable: whether XDP is enabled
+ *
+ * Use this when XDPSQs are not always available to dynamically enable
+ * and disable redirect feature.
+ */
+void libeth_xdp_set_redirect(struct net_device *dev, bool enable)
+{
+	if (enable)
+		xdp_features_set_redirect_target(dev, true);
+	else
+		xdp_features_clear_redirect_target(dev);
+}
+EXPORT_SYMBOL_GPL(libeth_xdp_set_redirect);
+
 /* Module */
 
 static const struct libeth_xdp_ops xdp_ops __initconst = {
diff --git a/include/net/libeth/xdp.h b/include/net/libeth/xdp.h
index 643b0a8acab3..f0b1160bee51 100644
--- a/include/net/libeth/xdp.h
+++ b/include/net/libeth/xdp.h
@@ -1624,6 +1624,51 @@ void name(struct libeth_xdp_tx_bulk *bq)				      \
 
 #define LIBETH_XDP_DEFINE_END()		__diag_pop()
 
+/* XMO */
+
+/**
+ * libeth_xdp_buff_to_rq - get RQ pointer from an XDP buffer pointer
+ * @xdp: &libeth_xdp_buff corresponding to the queue
+ * @type: typeof() of the driver Rx queue structure
+ * @member: name of &xdp_rxq_info inside @type
+ *
+ * Often times, pointer to the RQ is needed when reading/filling metadata from
+ * HW descriptors. The helper can be used to quickly jump from an XDP buffer
+ * to the queue corresponding to its &xdp_rxq_info without introducing
+ * additional fields (&libeth_xdp_buff is precisely 1 cacheline long on x64).
+ */
+#define libeth_xdp_buff_to_rq(xdp, type, member)			      \
+	container_of_const((xdp)->base.rxq, type, member)
+
+/**
+ * libeth_xdpmo_rx_hash - convert &libeth_rx_pt to an XDP RSS hash metadata
+ * @hash: pointer to the variable to write the hash to
+ * @rss_type: pointer to the variable to write the hash type to
+ * @val: hash value from the HW descriptor
+ * @pt: libeth parsed packet type
+ *
+ * Handle zeroed/non-available hash and convert libeth parsed packet type to
+ * the corresponding XDP RSS hash type. To be called at the end of
+ * xdp_metadata_ops idpf_xdpmo::xmo_rx_hash() implementation.
+ * Note that if the driver doesn't use a constant packet type lookup table but
+ * generates it at runtime, it must call libeth_rx_pt_gen_hash_type(pt) to
+ * generate XDP RSS hash type for each packet type.
+ *
+ * Return: 0 on success, -ENODATA when the hash is not available.
+ */
+static inline int libeth_xdpmo_rx_hash(u32 *hash,
+				       enum xdp_rss_hash_type *rss_type,
+				       u32 val, struct libeth_rx_pt pt)
+{
+	if (unlikely(!val))
+		return -ENODATA;
+
+	*hash = val;
+	*rss_type = pt.hash_type;
+
+	return 0;
+}
+
 /* Tx buffer completion */
 
 void libeth_xdp_return_buff_bulk(const struct skb_shared_info *sinfo,
@@ -1690,4 +1735,49 @@ static inline void libeth_xdp_complete_tx(struct libeth_sqe *sqe,
 	__libeth_xdp_complete_tx(sqe, cp, libeth_xdp_return_buff_bulk);
 }
 
+/* Misc */
+
+u32 libeth_xdp_queue_threshold(u32 count);
+
+void __libeth_xdp_set_features(struct net_device *dev,
+			       const struct xdp_metadata_ops *xmo);
+void libeth_xdp_set_redirect(struct net_device *dev, bool enable);
+
+/**
+ * libeth_xdp_set_features - set XDP features for netdev
+ * @dev: &net_device to configure
+ * @...: optional params, see __libeth_xdp_set_features()
+ *
+ * Set all the features libeth_xdp supports, including .ndo_xdp_xmit(). That
+ * said, it should be used only when XDPSQs are always available regardless
+ * of whether an XDP prog is attached to @dev.
+ */
+#define libeth_xdp_set_features(dev, ...)				      \
+	CONCATENATE(__libeth_xdp_feat,					      \
+		    COUNT_ARGS(__VA_ARGS__))(dev, ##__VA_ARGS__)
+
+#define __libeth_xdp_feat0(dev)						      \
+	__libeth_xdp_set_features(dev, NULL)
+#define __libeth_xdp_feat1(dev, xmo)					      \
+	__libeth_xdp_set_features(dev, xmo)
+
+/**
+ * libeth_xdp_set_features_noredir - enable all libeth_xdp features w/o redir
+ * @dev: target &net_device
+ * @...: optional params, see __libeth_xdp_set_features()
+ *
+ * Enable everything except the .ndo_xdp_xmit() feature, use when XDPSQs are
+ * not available right after netdev registration.
+ */
+#define libeth_xdp_set_features_noredir(dev, ...)			      \
+	__libeth_xdp_set_features_noredir(dev, __UNIQUE_ID(dev_),	      \
+					  ##__VA_ARGS__)
+
+#define __libeth_xdp_set_features_noredir(dev, ud, ...) do {		      \
+	struct net_device *ud = (dev);					      \
+									      \
+	libeth_xdp_set_features(ud, ##__VA_ARGS__);			      \
+	libeth_xdp_set_redirect(ud, false);				      \
+} while (0)
+
 #endif /* __LIBETH_XDP_H */
-- 
2.47.1