scsi: cxlflash: Support process element lifecycle

As part of the context lifecycle, the associated process element within the
Shared Process Area (SPA) of the link must be updated. Each process is defined
by various parameters (pid, tid, PASID mm) that are stored in the SPA upon
starting a context and invalidated when a context is stopped.

Use the OCXL provider services to configure the SPA with the appropriate data
that is unique to the process when starting a context. Initially only kernel
contexts are supported and therefore these process values are not applicable.
Note that the OCXL service used has an optional callback for translation fault
error notification. While not used here, it will be expanded in a future
commit.

Also add a service to stop a context by terminating the corresponding PASID
and remove the process element from the SPA.
Signed-off-by: Uma Krishnan <ukrishn@linux.vnet.ibm.com>
Acked-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/cxlflash/ocxl_hw.c

@@ -189,7 +189,7 @@ static int ocxlflash_process_element(void *ctx_cookie)
  * start_context() - local routine to start a context
  * @ctx:	Adapter context to be started.
  *
- * Assign the context specific MMIO space.
+ * Assign the context specific MMIO space, add and enable the PE.
  *
  * Return: 0 on success, -errno on failure
  */
@@ -197,7 +197,10 @@ static int start_context(struct ocxlflash_context *ctx)
 {
 	struct ocxl_hw_afu *afu = ctx->hw_afu;
 	struct ocxl_afu_config *acfg = &afu->acfg;
+	void *link_token = afu->link_token;
+	struct device *dev = afu->dev;
 	bool master = ctx->master;
+	int rc = 0;
 
 	if (master) {
 		ctx->psn_size = acfg->global_mmio_size;
@@ -207,7 +210,16 @@ static int start_context(struct ocxlflash_context *ctx)
 		ctx->psn_phys = afu->ppmmio_phys + (ctx->pe * ctx->psn_size);
 	}
 
-	return 0;
+
+	/* pid, tid, amr and mm are zeroes/NULL for a kernel context */
+	rc = ocxl_link_add_pe(link_token, ctx->pe, 0, 0, 0, NULL, NULL, NULL);
+	if (unlikely(rc)) {
+		dev_err(dev, "%s: ocxl_link_add_pe failed rc=%d\n",
+			__func__, rc);
+		goto out;
+	}
+out:
+	return rc;
 }
 
 /**
@@ -223,6 +235,41 @@ static int ocxlflash_start_context(void *ctx_cookie)
 	return start_context(ctx);
 }
 
+/**
+ * ocxlflash_stop_context() - stop a context
+ * @ctx_cookie:	Adapter context to be stopped.
+ *
+ * Return: 0 on success, -errno on failure
+ */
+static int ocxlflash_stop_context(void *ctx_cookie)
+{
+	struct ocxlflash_context *ctx = ctx_cookie;
+	struct ocxl_hw_afu *afu = ctx->hw_afu;
+	struct ocxl_afu_config *acfg = &afu->acfg;
+	struct pci_dev *pdev = afu->pdev;
+	struct device *dev = afu->dev;
+	int rc;
+
+	rc = ocxl_config_terminate_pasid(pdev, acfg->dvsec_afu_control_pos,
+					 ctx->pe);
+	if (unlikely(rc)) {
+		dev_err(dev, "%s: ocxl_config_terminate_pasid failed rc=%d\n",
+			__func__, rc);
+		/* If EBUSY, PE could be referenced in future by the AFU */
+		if (rc == -EBUSY)
+			goto out;
+	}
+
+	rc = ocxl_link_remove_pe(afu->link_token, ctx->pe);
+	if (unlikely(rc)) {
+		dev_err(dev, "%s: ocxl_link_remove_pe failed rc=%d\n",
+			__func__, rc);
+		goto out;
+	}
+out:
+	return rc;
+}
+
 /**
  * ocxlflash_set_master() - sets the context as master
  * @ctx_cookie:	Adapter context to set as master.
@@ -696,6 +743,7 @@ const struct cxlflash_backend_ops cxlflash_ocxl_ops = {
 	.psa_unmap		= ocxlflash_psa_unmap,
 	.process_element	= ocxlflash_process_element,
 	.start_context		= ocxlflash_start_context,
+	.stop_context		= ocxlflash_stop_context,
 	.set_master		= ocxlflash_set_master,
 	.get_context		= ocxlflash_get_context,
 	.dev_context_init	= ocxlflash_dev_context_init,