nvmet: Implement arbitration feature support

NVMe base specification v2.1 mandates support for the arbitration
feature (NVME_FEAT_ARBITRATION). Introduce the data structure
struct nvmet_feat_arbitration to define the high, medium and low
priority weight fields and the arbitration burst field of this feature
and implement the functions nvmet_get_feat_arbitration() and
nvmet_set_feat_arbitration() functions to get and set these fields.

Since there is no generic way to implement support for the arbitration
feature, these functions respectively use the controller get_feature()
and set_feature() operations to process the feature with the help of
the controller driver. If the controller driver does not implement these
operations and a get feature command or a set feature command for this
feature is received, the command is failed with an invalid field error.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Rick Wertenbroek <rick.wertenbroek@gmail.com>
Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Keith Busch <kbusch@kernel.org>

drivers/nvme/target/admin-cmd.c

@@ -1324,6 +1324,25 @@ static u16 nvmet_set_feat_irq_config(struct nvmet_req *req)
 	return ctrl->ops->set_feature(ctrl, NVME_FEAT_IRQ_CONFIG, &irqcfg);
 }
 
+static u16 nvmet_set_feat_arbitration(struct nvmet_req *req)
+{
+	struct nvmet_ctrl *ctrl = req->sq->ctrl;
+	u32 cdw11 = le32_to_cpu(req->cmd->common.cdw11);
+	struct nvmet_feat_arbitration arb = {
+		.hpw = (cdw11 >> 24) & 0xff,
+		.mpw = (cdw11 >> 16) & 0xff,
+		.lpw = (cdw11 >> 8) & 0xff,
+		.ab = cdw11 & 0x3,
+	};
+
+	if (!ctrl->ops->set_feature) {
+		req->error_loc = offsetof(struct nvme_common_command, cdw10);
+		return NVME_SC_INVALID_FIELD | NVME_STATUS_DNR;
+	}
+
+	return ctrl->ops->set_feature(ctrl, NVME_FEAT_ARBITRATION, &arb);
+}
+
 void nvmet_execute_set_features(struct nvmet_req *req)
 {
 	struct nvmet_subsys *subsys = nvmet_req_subsys(req);
@@ -1337,6 +1356,9 @@ void nvmet_execute_set_features(struct nvmet_req *req)
 		return;
 
 	switch (cdw10 & 0xff) {
+	case NVME_FEAT_ARBITRATION:
+		status = nvmet_set_feat_arbitration(req);
+		break;
 	case NVME_FEAT_NUM_QUEUES:
 		ncqr = (cdw11 >> 16) & 0xffff;
 		nsqr = cdw11 & 0xffff;
@@ -1446,6 +1468,30 @@ static u16 nvmet_get_feat_irq_config(struct nvmet_req *req)
 	return NVME_SC_SUCCESS;
 }
 
+static u16 nvmet_get_feat_arbitration(struct nvmet_req *req)
+{
+	struct nvmet_ctrl *ctrl = req->sq->ctrl;
+	struct nvmet_feat_arbitration arb = { };
+	u16 status;
+
+	if (!ctrl->ops->get_feature) {
+		req->error_loc = offsetof(struct nvme_common_command, cdw10);
+		return NVME_SC_INVALID_FIELD | NVME_STATUS_DNR;
+	}
+
+	status = ctrl->ops->get_feature(ctrl, NVME_FEAT_ARBITRATION, &arb);
+	if (status != NVME_SC_SUCCESS)
+		return status;
+
+	nvmet_set_result(req,
+			 ((u32)arb.hpw << 24) |
+			 ((u32)arb.mpw << 16) |
+			 ((u32)arb.lpw << 8) |
+			 (arb.ab & 0x3));
+
+	return NVME_SC_SUCCESS;
+}
+
 void nvmet_get_feat_kato(struct nvmet_req *req)
 {
 	nvmet_set_result(req, req->sq->ctrl->kato * 1000);
@@ -1472,8 +1518,6 @@ void nvmet_execute_get_features(struct nvmet_req *req)
 	 * need to come up with some fake values for these.
 	 */
 #if 0
-	case NVME_FEAT_ARBITRATION:
-		break;
 	case NVME_FEAT_POWER_MGMT:
 		break;
 	case NVME_FEAT_TEMP_THRESH:
@@ -1483,6 +1527,9 @@ void nvmet_execute_get_features(struct nvmet_req *req)
 	case NVME_FEAT_WRITE_ATOMIC:
 		break;
 #endif
+	case NVME_FEAT_ARBITRATION:
+		status = nvmet_get_feat_arbitration(req);
+		break;
 	case NVME_FEAT_IRQ_COALESCE:
 		status = nvmet_get_feat_irq_coalesce(req);
 		break;

drivers/nvme/target/nvmet.h

@@ -921,4 +921,11 @@ struct nvmet_feat_irq_config {
 	bool		cd;
 };
 
+struct nvmet_feat_arbitration {
+	u8		hpw;
+	u8		mpw;
+	u8		lpw;
+	u8		ab;
+};
+
 #endif /* _NVMET_H */