Re: [PATCH v12 11/26] nvme-tcp: Add modparam to control the ULP offload enablement

On 09/08/2023 11:03, Sagi Grimberg wrote:

On 7/12/23 19:14, Aurelien Aptel wrote:

quoted

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 <redacted>
Signed-off-by: Shai Malin <redacted>
Signed-off-by: Aurelien Aptel <redacted>
---
  drivers/nvme/host/tcp.c | 12 +++++++++++-
  1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index e68e5da3df76..e560bdf3a023 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c

@@ -49,6 +49,16 @@ MODULE_PARM_DESC(tls_handshake_timeout,

           "nvme TLS handshake timeout in seconds (default 10)");
  #endif
+#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");

the name is strange.
maybe call it ddp_offload?

Agree. ddp_offload is a better fit.

and in the description spell it as "direct data placement"

quoted

+#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

@@ -350,7 +360,7 @@ static bool nvme_tcp_ddp_query_limits(struct 

net_device *netdev,
  static inline bool is_netdev_ulp_offload_active(struct net_device 
*netdev,
                          struct nvme_tcp_queue *queue)
  {
-    if (!netdev || !queue)
+    if (!ulp_offload || !netdev || !queue)
          return false;
      /* If we cannot query the netdev limitations, do not offload */

This patch should be folded to the control path. No reason for it to
stand on its own I think.

Agree.