Commit 1dd0c0e4 authored by Matthew R. Ochs's avatar Matthew R. Ochs Committed by Martin K. Petersen
Browse files

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: default avatarMatthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: default avatarUma Krishnan <ukrishn@linux.vnet.ibm.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 3065267a

drivers/scsi/cxlflash/common.h

+11 −1
Original line number Diff line number Diff line
@@ -96,6 +96,13 @@ enum cxlflash_state { 
	STATE_FAILTERM	/* Failed/terminating state, error out users/threads */

};



enum cxlflash_hwq_mode {

	HWQ_MODE_RR,	/* Roundrobin (default) */

	HWQ_MODE_TAG,	/* Distribute based on block MQ tag */

	HWQ_MODE_CPU,	/* CPU affinity */

	MAX_HWQ_MODE

};



/*

 * Each context has its own set of resource handles that is visible

 * only from that context.
@@ -146,9 +153,9 @@ struct afu_cmd { 
	struct scsi_cmnd *scp;

	struct completion cevent;

	struct list_head queue;

	u32 hwq_index;



	u8 cmd_tmf:1;

	u32 hwq_index;



	/* As per the SISLITE spec the IOARCB EA has to be 16-byte aligned.

	 * However for performance reasons the IOARCB/IOASA should be
@@ -213,8 +220,11 @@ struct afu { 
	atomic_t cmds_active;	/* Number of currently active AFU commands */

	u64 hb;

	u32 internal_lun;	/* User-desired LUN mode for this AFU */



	u32 num_hwqs;		/* Number of hardware queues */

	u32 desired_hwqs;	/* Desired h/w queues, effective on AFU reset */

	enum cxlflash_hwq_mode hwq_mode; /* Steering mode for h/w queues */

	u32 hwq_rr_count;	/* Count to distribute traffic for roundrobin */



	char version[16];

	u64 interface_version;

drivers/scsi/cxlflash/main.c

+115 −5
Original line number Diff line number Diff line
@@ -357,6 +357,43 @@ static int wait_resp(struct afu *afu, struct afu_cmd *cmd) 
	return rc;

}



/**

 * cmd_to_target_hwq() - selects a target hardware queue for a SCSI command

 * @host:	SCSI host associated with device.

 * @scp:	SCSI command to send.

 * @afu:	SCSI command to send.

 *

 * Hashes a command based upon the hardware queue mode.

 *

 * Return: Trusted index of target hardware queue

 */

static u32 cmd_to_target_hwq(struct Scsi_Host *host, struct scsi_cmnd *scp,

			     struct afu *afu)

{

	u32 tag;

	u32 hwq = 0;



	if (afu->num_hwqs == 1)

		return 0;



	switch (afu->hwq_mode) {

	case HWQ_MODE_RR:

		hwq = afu->hwq_rr_count++ % afu->num_hwqs;

		break;

	case HWQ_MODE_TAG:

		tag = blk_mq_unique_tag(scp->request);

		hwq = blk_mq_unique_tag_to_hwq(tag);

		break;

	case HWQ_MODE_CPU:

		hwq = smp_processor_id() % afu->num_hwqs;

		break;

	default:

		WARN_ON_ONCE(1);

	}



	return hwq;

}



/**

 * send_tmf() - sends a Task Management Function (TMF)

 * @afu:	AFU to checkout from.
@@ -368,10 +405,12 @@ static int wait_resp(struct afu *afu, struct afu_cmd *cmd) 
 */

static int send_tmf(struct afu *afu, struct scsi_cmnd *scp, u64 tmfcmd)

{

	struct cxlflash_cfg *cfg = shost_priv(scp->device->host);

	struct Scsi_Host *host = scp->device->host;

	struct cxlflash_cfg *cfg = shost_priv(host);

	struct afu_cmd *cmd = sc_to_afucz(scp);

	struct device *dev = &cfg->dev->dev;

	struct hwq *hwq = get_hwq(afu, PRIMARY_HWQ);

	int hwq_index = cmd_to_target_hwq(host, scp, afu);

	struct hwq *hwq = get_hwq(afu, hwq_index);

	ulong lock_flags;

	int rc = 0;

	ulong to;
@@ -388,7 +427,7 @@ static int send_tmf(struct afu *afu, struct scsi_cmnd *scp, u64 tmfcmd) 
	cmd->scp = scp;

	cmd->parent = afu;

	cmd->cmd_tmf = true;

	cmd->hwq_index = hwq->index;

	cmd->hwq_index = hwq_index;



	cmd->rcb.ctx_id = hwq->ctx_hndl;

	cmd->rcb.msi = SISL_MSI_RRQ_UPDATED;
@@ -448,7 +487,8 @@ static int cxlflash_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scp) 
	struct device *dev = &cfg->dev->dev;

	struct afu_cmd *cmd = sc_to_afucz(scp);

	struct scatterlist *sg = scsi_sglist(scp);

	struct hwq *hwq = get_hwq(afu, PRIMARY_HWQ);

	int hwq_index = cmd_to_target_hwq(host, scp, afu);

	struct hwq *hwq = get_hwq(afu, hwq_index);

	u16 req_flags = SISL_REQ_FLAGS_SUP_UNDERRUN;

	ulong lock_flags;

	int rc = 0;
@@ -498,7 +538,7 @@ static int cxlflash_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scp) 


	cmd->scp = scp;

	cmd->parent = afu;

	cmd->hwq_index = hwq->index;

	cmd->hwq_index = hwq_index;



	cmd->rcb.ctx_id = hwq->ctx_hndl;

	cmd->rcb.msi = SISL_MSI_RRQ_UPDATED;
@@ -2654,6 +2694,74 @@ retry: 
	return count;

}



static const char *hwq_mode_name[MAX_HWQ_MODE] = { "rr", "tag", "cpu" };



/**

 * hwq_mode_show() - presents the HWQ steering mode for the host

 * @dev:	Generic device associated with the host.

 * @attr:	Device attribute representing the HWQ steering mode.

 * @buf:	Buffer of length PAGE_SIZE to report back the HWQ steering mode

 *		as a character string.

 *

 * Return: The size of the ASCII string returned in @buf.

 */

static ssize_t hwq_mode_show(struct device *dev,

			     struct device_attribute *attr, char *buf)

{

	struct cxlflash_cfg *cfg = shost_priv(class_to_shost(dev));

	struct afu *afu = cfg->afu;



	return scnprintf(buf, PAGE_SIZE, "%s\n", hwq_mode_name[afu->hwq_mode]);

}



/**

 * hwq_mode_store() - sets the HWQ steering mode for the host

 * @dev:	Generic device associated with the host.

 * @attr:	Device attribute representing the HWQ steering mode.

 * @buf:	Buffer of length PAGE_SIZE containing the HWQ steering mode

 *		as a character string.

 * @count:	Length of data resizing in @buf.

 *

 * rr = Round-Robin

 * tag = Block MQ Tagging

 * cpu = CPU Affinity

 *

 * Return: The size of the ASCII string returned in @buf.

 */

static ssize_t hwq_mode_store(struct device *dev,

			      struct device_attribute *attr,

			      const char *buf, size_t count)

{

	struct Scsi_Host *shost = class_to_shost(dev);

	struct cxlflash_cfg *cfg = shost_priv(shost);

	struct device *cfgdev = &cfg->dev->dev;

	struct afu *afu = cfg->afu;

	int i;

	u32 mode = MAX_HWQ_MODE;



	for (i = 0; i < MAX_HWQ_MODE; i++) {

		if (!strncmp(hwq_mode_name[i], buf, strlen(hwq_mode_name[i]))) {

			mode = i;

			break;

		}

	}



	if (mode >= MAX_HWQ_MODE) {

		dev_info(cfgdev, "Invalid HWQ steering mode.\n");

		return -EINVAL;

	}



	if ((mode == HWQ_MODE_TAG) && !shost_use_blk_mq(shost)) {

		dev_info(cfgdev, "SCSI-MQ is not enabled, use a different "

			 "HWQ steering mode.\n");

		return -EINVAL;

	}



	afu->hwq_mode = mode;



	return count;

}



/**

 * mode_show() - presents the current mode of the device

 * @dev:	Generic device associated with the device.
@@ -2686,6 +2794,7 @@ static DEVICE_ATTR_RO(port2_lun_table); 
static DEVICE_ATTR_RO(port3_lun_table);

static DEVICE_ATTR_RW(irqpoll_weight);

static DEVICE_ATTR_RW(num_hwqs);

static DEVICE_ATTR_RW(hwq_mode);



static struct device_attribute *cxlflash_host_attrs[] = {

	&dev_attr_port0,
@@ -2700,6 +2809,7 @@ static struct device_attribute *cxlflash_host_attrs[] = { 
	&dev_attr_port3_lun_table,

	&dev_attr_irqpoll_weight,

	&dev_attr_num_hwqs,

	&dev_attr_hwq_mode,

	NULL

};

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