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    SubjectRe: [PATCH v2 17/17] ibmvfc: provide modules parameters for MQ settings
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    On 12/2/20 10:40 AM, Brian King wrote:
    > On 12/1/20 6:53 PM, Tyrel Datwyler wrote:
    >> +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.

    >
    >> +
    >> 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) "]");
    >
    >> @@ -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

    >
    >> + 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);
    >
    >
    >

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