scsi: cxlflash: Introduce hardware queue steering
As an enhancement to distribute requests to multiple hardware queues, add the infrastructure to hash a SCSI command into a particular hardware queue. Support the following scenarios when deriving which queue to use: single queue, tagging when SCSI-MQ enabled, and simple hash via CPU ID when SCSI-MQ is disabled. Rather than altering the existing send API, the derived hardware queue is stored in the AFU command where it can be used for sending a command to the chosen hardware queue. Signed-off-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com> Signed-off-by: Uma Krishnan <ukrishn@linux.vnet.ibm.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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3065267a80
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@ -96,6 +96,13 @@ enum cxlflash_state {
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STATE_FAILTERM /* Failed/terminating state, error out users/threads */
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};
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enum cxlflash_hwq_mode {
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HWQ_MODE_RR, /* Roundrobin (default) */
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HWQ_MODE_TAG, /* Distribute based on block MQ tag */
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HWQ_MODE_CPU, /* CPU affinity */
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MAX_HWQ_MODE
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};
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/*
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* Each context has its own set of resource handles that is visible
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* only from that context.
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@ -146,9 +153,9 @@ struct afu_cmd {
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struct scsi_cmnd *scp;
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struct completion cevent;
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struct list_head queue;
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u32 hwq_index;
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u8 cmd_tmf:1;
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u32 hwq_index;
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/* As per the SISLITE spec the IOARCB EA has to be 16-byte aligned.
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* However for performance reasons the IOARCB/IOASA should be
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@ -213,8 +220,11 @@ struct afu {
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atomic_t cmds_active; /* Number of currently active AFU commands */
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u64 hb;
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u32 internal_lun; /* User-desired LUN mode for this AFU */
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u32 num_hwqs; /* Number of hardware queues */
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u32 desired_hwqs; /* Desired h/w queues, effective on AFU reset */
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enum cxlflash_hwq_mode hwq_mode; /* Steering mode for h/w queues */
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u32 hwq_rr_count; /* Count to distribute traffic for roundrobin */
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char version[16];
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u64 interface_version;
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@ -357,6 +357,43 @@ static int wait_resp(struct afu *afu, struct afu_cmd *cmd)
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return rc;
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}
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/**
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* cmd_to_target_hwq() - selects a target hardware queue for a SCSI command
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* @host: SCSI host associated with device.
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* @scp: SCSI command to send.
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* @afu: SCSI command to send.
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*
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* Hashes a command based upon the hardware queue mode.
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*
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* Return: Trusted index of target hardware queue
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*/
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static u32 cmd_to_target_hwq(struct Scsi_Host *host, struct scsi_cmnd *scp,
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struct afu *afu)
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{
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u32 tag;
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u32 hwq = 0;
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if (afu->num_hwqs == 1)
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return 0;
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switch (afu->hwq_mode) {
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case HWQ_MODE_RR:
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hwq = afu->hwq_rr_count++ % afu->num_hwqs;
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break;
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case HWQ_MODE_TAG:
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tag = blk_mq_unique_tag(scp->request);
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hwq = blk_mq_unique_tag_to_hwq(tag);
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break;
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case HWQ_MODE_CPU:
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hwq = smp_processor_id() % afu->num_hwqs;
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break;
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default:
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WARN_ON_ONCE(1);
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}
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return hwq;
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}
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/**
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* send_tmf() - sends a Task Management Function (TMF)
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* @afu: AFU to checkout from.
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@ -368,10 +405,12 @@ static int wait_resp(struct afu *afu, struct afu_cmd *cmd)
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*/
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static int send_tmf(struct afu *afu, struct scsi_cmnd *scp, u64 tmfcmd)
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{
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struct cxlflash_cfg *cfg = shost_priv(scp->device->host);
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struct Scsi_Host *host = scp->device->host;
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struct cxlflash_cfg *cfg = shost_priv(host);
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struct afu_cmd *cmd = sc_to_afucz(scp);
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struct device *dev = &cfg->dev->dev;
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struct hwq *hwq = get_hwq(afu, PRIMARY_HWQ);
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int hwq_index = cmd_to_target_hwq(host, scp, afu);
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struct hwq *hwq = get_hwq(afu, hwq_index);
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ulong lock_flags;
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int rc = 0;
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ulong to;
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@ -388,7 +427,7 @@ static int send_tmf(struct afu *afu, struct scsi_cmnd *scp, u64 tmfcmd)
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cmd->scp = scp;
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cmd->parent = afu;
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cmd->cmd_tmf = true;
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cmd->hwq_index = hwq->index;
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cmd->hwq_index = hwq_index;
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cmd->rcb.ctx_id = hwq->ctx_hndl;
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cmd->rcb.msi = SISL_MSI_RRQ_UPDATED;
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@ -448,7 +487,8 @@ static int cxlflash_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scp)
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struct device *dev = &cfg->dev->dev;
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struct afu_cmd *cmd = sc_to_afucz(scp);
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struct scatterlist *sg = scsi_sglist(scp);
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struct hwq *hwq = get_hwq(afu, PRIMARY_HWQ);
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int hwq_index = cmd_to_target_hwq(host, scp, afu);
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struct hwq *hwq = get_hwq(afu, hwq_index);
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u16 req_flags = SISL_REQ_FLAGS_SUP_UNDERRUN;
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ulong lock_flags;
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int rc = 0;
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@ -498,7 +538,7 @@ static int cxlflash_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scp)
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cmd->scp = scp;
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cmd->parent = afu;
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cmd->hwq_index = hwq->index;
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cmd->hwq_index = hwq_index;
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cmd->rcb.ctx_id = hwq->ctx_hndl;
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cmd->rcb.msi = SISL_MSI_RRQ_UPDATED;
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@ -2654,6 +2694,74 @@ retry:
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return count;
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}
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static const char *hwq_mode_name[MAX_HWQ_MODE] = { "rr", "tag", "cpu" };
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/**
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* hwq_mode_show() - presents the HWQ steering mode for the host
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* @dev: Generic device associated with the host.
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* @attr: Device attribute representing the HWQ steering mode.
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* @buf: Buffer of length PAGE_SIZE to report back the HWQ steering mode
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* as a character string.
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*
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* Return: The size of the ASCII string returned in @buf.
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*/
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static ssize_t hwq_mode_show(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct cxlflash_cfg *cfg = shost_priv(class_to_shost(dev));
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struct afu *afu = cfg->afu;
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return scnprintf(buf, PAGE_SIZE, "%s\n", hwq_mode_name[afu->hwq_mode]);
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}
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/**
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* hwq_mode_store() - sets the HWQ steering mode for the host
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* @dev: Generic device associated with the host.
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* @attr: Device attribute representing the HWQ steering mode.
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* @buf: Buffer of length PAGE_SIZE containing the HWQ steering mode
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* as a character string.
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* @count: Length of data resizing in @buf.
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*
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* rr = Round-Robin
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* tag = Block MQ Tagging
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* cpu = CPU Affinity
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*
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* Return: The size of the ASCII string returned in @buf.
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*/
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static ssize_t hwq_mode_store(struct device *dev,
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struct device_attribute *attr,
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const char *buf, size_t count)
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{
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struct Scsi_Host *shost = class_to_shost(dev);
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struct cxlflash_cfg *cfg = shost_priv(shost);
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struct device *cfgdev = &cfg->dev->dev;
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struct afu *afu = cfg->afu;
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int i;
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u32 mode = MAX_HWQ_MODE;
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for (i = 0; i < MAX_HWQ_MODE; i++) {
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if (!strncmp(hwq_mode_name[i], buf, strlen(hwq_mode_name[i]))) {
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mode = i;
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break;
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}
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}
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if (mode >= MAX_HWQ_MODE) {
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dev_info(cfgdev, "Invalid HWQ steering mode.\n");
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return -EINVAL;
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}
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if ((mode == HWQ_MODE_TAG) && !shost_use_blk_mq(shost)) {
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dev_info(cfgdev, "SCSI-MQ is not enabled, use a different "
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"HWQ steering mode.\n");
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return -EINVAL;
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}
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afu->hwq_mode = mode;
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return count;
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}
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/**
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* mode_show() - presents the current mode of the device
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* @dev: Generic device associated with the device.
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@ -2686,6 +2794,7 @@ static DEVICE_ATTR_RO(port2_lun_table);
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static DEVICE_ATTR_RO(port3_lun_table);
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static DEVICE_ATTR_RW(irqpoll_weight);
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static DEVICE_ATTR_RW(num_hwqs);
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static DEVICE_ATTR_RW(hwq_mode);
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static struct device_attribute *cxlflash_host_attrs[] = {
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&dev_attr_port0,
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@ -2700,6 +2809,7 @@ static struct device_attribute *cxlflash_host_attrs[] = {
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&dev_attr_port3_lun_table,
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&dev_attr_irqpoll_weight,
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&dev_attr_num_hwqs,
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&dev_attr_hwq_mode,
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NULL
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};
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