scsi: lpfc: Work around NVME cmd iu SGL type

The hardware offload for NVME commands was created when the
FC-NVME standard was setting SGL Descriptor Type to SGL Data
Block Descriptor (0h) and SGL Descriptor Sub Type to Address (0h).

A late change in NVMe-over-Fabrics obsoleted these values, creating
a transport SGL descriptor type with new values to go into these
fields.

For initial hardware support, in order to be compliant to the spec,
use host-supplied cmd IU buffers instead of the adapter generated
values. Later hardware will correct this.

Add a module parameter to override this offload disablement if looking
for lowest latency. This is reasonable as nothing in FC-NVME uses
the SQE SGL values.

Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/scsi/lpfc/lpfc_attr.c b/drivers/scsi/lpfc/lpfc_attr.c
index 14f6efcf8f0b..46f6d97d21d6 100644
--- a/drivers/scsi/lpfc/lpfc_attr.c
+++ b/drivers/scsi/lpfc/lpfc_attr.c
@@ -5042,6 +5042,18 @@ LPFC_ATTR_RW(nvme_oas, 0, 0, 1,
 	     "Use OAS bit on NVME IOs");
 
 /*
+ * lpfc_nvme_embed_cmd: Use the oas bit when sending NVME/NVMET IOs
+ *
+ *      0  = Put NVME Command in SGL
+ *      1  = Embed NVME Command in WQE (unless G7)
+ *      2 =  Embed NVME Command in WQE (force)
+ *
+ * Value range is [0,2]. Default value is 1.
+ */
+LPFC_ATTR_RW(nvme_embed_cmd, 1, 0, 2,
+	     "Embed NVME Command in WQE");
+
+/*
  * lpfc_fcp_io_channel: Set the number of FCP IO channels the driver
  * will advertise it supports to the SCSI layer. This also will map to
  * the number of WQs the driver will create.
@@ -5282,6 +5294,7 @@ struct device_attribute *lpfc_hba_attrs[] = {
 	&dev_attr_lpfc_task_mgmt_tmo,
 	&dev_attr_lpfc_use_msi,
 	&dev_attr_lpfc_nvme_oas,
+	&dev_attr_lpfc_nvme_embed_cmd,
 	&dev_attr_lpfc_auto_imax,
 	&dev_attr_lpfc_fcp_imax,
 	&dev_attr_lpfc_fcp_cpu_map,
@@ -6306,6 +6319,7 @@ lpfc_get_cfgparam(struct lpfc_hba *phba)
 	lpfc_enable_SmartSAN_init(phba, lpfc_enable_SmartSAN);
 	lpfc_use_msi_init(phba, lpfc_use_msi);
 	lpfc_nvme_oas_init(phba, lpfc_nvme_oas);
+	lpfc_nvme_embed_cmd_init(phba, lpfc_nvme_embed_cmd);
 	lpfc_auto_imax_init(phba, lpfc_auto_imax);
 	lpfc_fcp_imax_init(phba, lpfc_fcp_imax);
 	lpfc_fcp_cpu_map_init(phba, lpfc_fcp_cpu_map);