On 12/2/20 10:40 AM, Brian King wrote:

On 12/1/20 6:53 PM, Tyrel Datwyler wrote:

quoted

+module_param_named(mig_channels_only, mig_channels_only, uint, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(mig_channels_only, "Prevent migration to non-channelized system. "
+		 "[Default=" __stringify(IBMVFC_MIG_NO_SUB_TO_CRQ) "]");
+module_param_named(mig_no_less_channels, mig_no_less_channels, uint, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(mig_no_less_channels, "Prevent migration to system with less channels. "
+		 "[Default=" __stringify(IBMVFC_MIG_NO_N_TO_M) "]");

Both of these are writeable, but it doesn't look like you do any re-negotiation
with the VIOS for these changed settings to take effect if someone changes
them at runtime.

For some reason I convinced myself that these could just be changed on the fly,
but yes for them to actually take effect we need to re-negotiate the channels setup.

quoted

+
 module_param_named(init_timeout, init_timeout, uint, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(init_timeout, "Initialization timeout in seconds. "
 		 "[Default=" __stringify(IBMVFC_INIT_TIMEOUT) "]");

quoted

@@ -3228,6 +3250,36 @@ static ssize_t ibmvfc_store_log_level(struct device *dev,
 	return strlen(buf);
 }
 
+static ssize_t ibmvfc_show_scsi_channels(struct device *dev,
+					 struct device_attribute *attr, char *buf)
+{
+	struct Scsi_Host *shost = class_to_shost(dev);
+	struct ibmvfc_host *vhost = shost_priv(shost);
+	unsigned long flags = 0;
+	int len;
+
+	spin_lock_irqsave(shost->host_lock, flags);
+	len = snprintf(buf, PAGE_SIZE, "%d\n", vhost->client_scsi_channels);
+	spin_unlock_irqrestore(shost->host_lock, flags);
+	return len;
+}
+
+static ssize_t ibmvfc_store_scsi_channels(struct device *dev,
+					 struct device_attribute *attr,
+					 const char *buf, size_t count)
+{
+	struct Scsi_Host *shost = class_to_shost(dev);
+	struct ibmvfc_host *vhost = shost_priv(shost);
+	unsigned long flags = 0;
+	unsigned int channels;
+
+	spin_lock_irqsave(shost->host_lock, flags);
+	channels = simple_strtoul(buf, NULL, 10);
+	vhost->client_scsi_channels = min(channels, nr_scsi_hw_queues);

Don't we need to do a LIP here for this new setting to go into effect?

Actually, we need a hard reset to break the CRQ Pair. A LIP will only do a NPIV
Logout/Login which keeps the existing channel setup.

-Tyrel

quoted

+	spin_unlock_irqrestore(shost->host_lock, flags);
+	return strlen(buf);
+}
+
 static DEVICE_ATTR(partition_name, S_IRUGO, ibmvfc_show_host_partition_name, NULL);
 static DEVICE_ATTR(device_name, S_IRUGO, ibmvfc_show_host_device_name, NULL);
 static DEVICE_ATTR(port_loc_code, S_IRUGO, ibmvfc_show_host_loc_code, NULL);