From: "Matthew R. Ochs" <mro...@linux.vnet.ibm.com>
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 <mro...@linux.vnet.ibm.com>
Signed-off-by: Uma Krishnan <ukri...@linux.vnet.ibm.com>
---
drivers/scsi/cxlflash/common.h | 12 ++++-
drivers/scsi/cxlflash/main.c | 120 +++++++++++++++++++++++++++++++++++++++--
2 files changed, 126 insertions(+), 6 deletions(-)
diff --git a/drivers/scsi/cxlflash/common.h b/drivers/scsi/cxlflash/common.h
index 8fd7a1f..256af81 100644
--- a/drivers/scsi/cxlflash/common.h
+++ b/drivers/scsi/cxlflash/common.h
@@ -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;
diff --git a/drivers/scsi/cxlflash/main.c b/drivers/scsi/cxlflash/main.c
index 113797a..a7d57c3 100644
--- a/drivers/scsi/cxlflash/main.c
+++ b/drivers/scsi/cxlflash/main.c
@@ -358,6 +358,43 @@ static int wait_resp(struct afu *afu, struct afu_cmd *cmd)
}
/**
+ * 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.
* @scp: SCSI command from stack.
@@ -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 @@ static ssize_t num_hwqs_store(struct device *dev,
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
};
--
2.1.0
