[PATCH v6 09/23] nvme-tcp: Add ulp_offload modparam to control enablement of ULP offload

[Aurelien Aptel <aaptel@nvidia.com>]

Add ulp_offload module parameter to the nvme-tcp module to control
ULP offload at the NVMe-TCP layer.

Turn ULP offload off be default, regardless of the NIC driver support.

In summary, to enable ULP offload:
- nvme-tcp modparam must be set to 1
- the NIC driver must set
  - NETIF_F_HW_ULP_DDP flag in netdev->features
  - ULP_DDP_C_NVME_TCP and/or ULP_DDP_C_NVME_TCP_DDGST_RX
    flags in ulp_limits->offload_capabilities

Signed-off-by: Yoray Zack <yorayz@nvidia.com>
Signed-off-by: Shai Malin <smalin@nvidia.com>
Signed-off-by: Aurelien Aptel <aaptel@nvidia.com>
---
 drivers/nvme/host/tcp.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 11d9197f59ab..7ee14b8a392e 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -34,6 +34,17 @@ static int so_priority;
 module_param(so_priority, int, 0644);
 MODULE_PARM_DESC(so_priority, "nvme tcp socket optimize priority");
 
+#ifdef CONFIG_ULP_DDP
+/* NVMeTCP direct data placement and data digest offload will not
+ * happen if this parameter false (default), regardless of what the
+ * underlying netdev capabilities are.
+ */
+static bool ulp_offload;
+module_param(ulp_offload, bool, 0644);
+MODULE_PARM_DESC(ulp_offload, "Enable or disable NVMeTCP ULP support");
+#endif
+
+
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 /* lockdep can detect a circular dependency of the form
  *   sk_lock -> mmap_lock (page fault) -> fs locks -> sk_lock
@@ -298,6 +309,9 @@ static bool nvme_tcp_ddp_query_limits(struct net_device *netdev,
 {
 	int ret;
 
+	if (!ulp_offload)
+		return false;
+
 	if (!netdev || !(netdev->features & NETIF_F_HW_ULP_DDP) ||
 	    !netdev->ulp_ddp_ops || !netdev->ulp_ddp_ops->ulp_ddp_limits)
 		return false;
@@ -497,6 +511,9 @@ static int nvme_tcp_offload_limits(struct nvme_tcp_queue *queue, struct net_devi
 {
 	struct nvme_tcp_ddp_limits limits = {{ULP_DDP_NVME}};
 
+	if (!ulp_offload)
+		return 0;
+
 	if (!nvme_tcp_ddp_query_limits(netdev, &limits)) {
 		queue->ctrl->offloading_netdev = NULL;
 		return -EOPNOTSUPP;
-- 
2.31.1