Subject: [PATCH v10 11/25] nvme-tcp: Add modparam to control the ULP offload enablement

From: Aurelien Aptel <[email-masked]>
Date: Thu, 26 Jan 2023 18:21:22 +0200

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.

Overall, in order to enable ULP offload:
- nvme-tcp ulp_offload modparam must be set to 1
- netdev->ulp_ddp_caps.active must have ULP_DDP_C_NVME_TCP and/or
  ULP_DDP_C_NVME_TCP_DDGST_RX capabilities flag set.

Signed-off-by: Yoray Zack <[email-masked]>
Signed-off-by: Shai Malin <[email-masked]>
Signed-off-by: Aurelien Aptel <[email-masked]>
---
 drivers/nvme/host/tcp.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 732f7636a6fc..77422f49fc76 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -35,6 +35,16 @@ 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
@@ -317,6 +327,9 @@ static bool nvme_tcp_ddp_query_limits(struct net_device *netdev,
 {
 	int ret;
 
+	if (!ulp_offload)
+		return false;
+
 	if (!netdev || !is_netdev_ulp_offload_active(netdev, NULL) ||
 	    !netdev->netdev_ops->ulp_ddp_ops->limits)
 		return false;
@@ -456,6 +469,9 @@ static int nvme_tcp_offload_socket(struct nvme_tcp_queue *queue)
 					 netdev->ulp_ddp_caps.active);
 	int ret;
 
+	if (!ulp_offload)
+		return 0;
+
 	config.nvmeotcp.pfv = NVME_TCP_PFV_1_0;
 	config.nvmeotcp.cpda = 0;
 	config.nvmeotcp.dgst =
@@ -510,6 +526,9 @@ static void nvme_tcp_offload_limits(struct nvme_tcp_queue *queue,
 {
 	struct ulp_ddp_limits limits = {.type = ULP_DDP_NVME };
 
+	if (!ulp_offload)
+		return;
+
 	if (!nvme_tcp_ddp_query_limits(netdev, &limits)) {
 		queue->ctrl->offloading_netdev = NULL;
 		return;
-- 
2.31.1