scsi: mpt3sas: Add support for shared host tagset for CPU hotplug

MPT Fusion adapters can steer completions to individual queues and we now
have support for shared host-wide tags in the I/O stack. The addition of
the host-wide tags allows us to enable multiqueue support for MPT Fusion
adapters. Once host-wise tags are enabled, the CPU hotplug feature is also
supported.

Allow use of host-wide tags to be disabled through the "host_tagset_enable"
module parameter. Once we do not have any major performance regressions
using host-wide tags, we will drop the hand-crafted interrupt affinity
settings.

Performance is meeting expectations. About 3.1M IOPS using 24 Drive SSD on
Aero controllers.

Link: https://lore.kernel.org/r/20210202095832.23072-1-sreekanth.reddy@broadcom.com
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/mpt3sas/mpt3sas_base.c

@@ -3648,25 +3648,16 @@ _base_get_msix_index(struct MPT3SAS_ADAPTER *ioc,
 		    base_mod64(atomic64_add_return(1,
 		    &ioc->total_io_cnt), ioc->reply_queue_count) : 0;
 
-	return ioc->cpu_msix_table[raw_smp_processor_id()];
-}
+	if (scmd && ioc->shost->nr_hw_queues > 1) {
+		u32 tag = blk_mq_unique_tag(scmd->request);
 
-/**
- * _base_sdev_nr_inflight_request -get number of inflight requests
- *				   of a request queue.
- * @q: request_queue object
- *
- * returns number of inflight request of a request queue.
- */
-inline unsigned long
-_base_sdev_nr_inflight_request(struct request_queue *q)
-{
-	struct blk_mq_hw_ctx *hctx = q->queue_hw_ctx[0];
+		return blk_mq_unique_tag_to_hwq(tag) +
+			ioc->high_iops_queues;
+	}
 
-	return atomic_read(&hctx->nr_active);
+	return ioc->cpu_msix_table[raw_smp_processor_id()];
 }
 
-
 /**
  * _base_get_high_iops_msix_index - get the msix index of
  *				high iops queues
@@ -3686,7 +3677,8 @@ _base_get_high_iops_msix_index(struct MPT3SAS_ADAPTER *ioc,
 	 * reply queues in terms of batch count 16 when outstanding
 	 * IOs on the target device is >=8.
 	 */
-	if (_base_sdev_nr_inflight_request(scmd->device->request_queue) >
+
+	if (atomic_read(&scmd->device->device_busy) >
 	    MPT3SAS_DEVICE_HIGH_IOPS_DEPTH)
 		return base_mod64((
 		    atomic64_add_return(1, &ioc->high_iops_outstanding) /
@@ -3739,8 +3731,23 @@ mpt3sas_base_get_smid_scsiio(struct MPT3SAS_ADAPTER *ioc, u8 cb_idx,
 	struct scsi_cmnd *scmd)
 {
 	struct scsiio_tracker *request = scsi_cmd_priv(scmd);
-	unsigned int tag = scmd->request->tag;
 	u16 smid;
+	u32 tag, unique_tag;
+
+	unique_tag = blk_mq_unique_tag(scmd->request);
+	tag = blk_mq_unique_tag_to_tag(unique_tag);
+
+	/*
+	 * Store hw queue number corresponding to the tag.
+	 * This hw queue number is used later to determine
+	 * the unique_tag using the logic below. This unique_tag
+	 * is used to retrieve the scmd pointer corresponding
+	 * to tag using scsi_host_find_tag() API.
+	 *
+	 * tag = smid - 1;
+	 * unique_tag = ioc->io_queue_num[tag] << BLK_MQ_UNIQUE_TAG_BITS | tag;
+	 */
+	ioc->io_queue_num[tag] = blk_mq_unique_tag_to_hwq(unique_tag);
 
 	smid = tag + 1;
 	request->cb_idx = cb_idx;
@@ -3831,6 +3838,7 @@ mpt3sas_base_free_smid(struct MPT3SAS_ADAPTER *ioc, u16 smid)
 
 		mpt3sas_base_clear_st(ioc, st);
 		_base_recovery_check(ioc);
+		ioc->io_queue_num[smid - 1] = 0;
 		return;
 	}
 
@@ -5362,6 +5370,9 @@ _base_release_memory_pools(struct MPT3SAS_ADAPTER *ioc)
 		kfree(ioc->chain_lookup);
 		ioc->chain_lookup = NULL;
 	}
+
+	kfree(ioc->io_queue_num);
+	ioc->io_queue_num = NULL;
 }
 
 /**
@@ -5773,6 +5784,11 @@ _base_allocate_memory_pools(struct MPT3SAS_ADAPTER *ioc)
 		    ioc_info(ioc, "internal(0x%p): depth(%d), start smid(%d)\n",
 			     ioc->internal,
 			     ioc->internal_depth, ioc->internal_smid));
+
+	ioc->io_queue_num = kcalloc(ioc->scsiio_depth,
+	    sizeof(u16), GFP_KERNEL);
+	if (!ioc->io_queue_num)
+		goto out;
 	/*
 	 * The number of NVMe page sized blocks needed is:
 	 *     (((sg_tablesize * 8) - 1) / (page_size - 8)) + 1

drivers/scsi/mpt3sas/mpt3sas_base.h

@@ -1439,6 +1439,7 @@ struct MPT3SAS_ADAPTER {
 	spinlock_t	scsi_lookup_lock;
 	int		pending_io_count;
 	wait_queue_head_t reset_wq;
+	u16		*io_queue_num;
 
 	/* PCIe SGL */
 	struct dma_pool *pcie_sgl_dma_pool;

drivers/scsi/mpt3sas/mpt3sas_scsih.c

@@ -54,6 +54,7 @@
 #include <linux/interrupt.h>
 #include <linux/aer.h>
 #include <linux/raid_class.h>
+#include <linux/blk-mq-pci.h>
 #include <asm/unaligned.h>
 
 #include "mpt3sas_base.h"
@@ -168,6 +169,11 @@ MODULE_PARM_DESC(multipath_on_hba,
 	"\t SAS 2.0 & SAS 3.0 HBA - This will be disabled,\n\t\t"
 	"\t SAS 3.5 HBA - This will be enabled)");
 
+static int host_tagset_enable = 1;
+module_param(host_tagset_enable, int, 0444);
+MODULE_PARM_DESC(host_tagset_enable,
+	"Shared host tagset enable/disable Default: enable(1)");
+
 /* raid transport support */
 static struct raid_template *mpt3sas_raid_template;
 static struct raid_template *mpt2sas_raid_template;
@@ -1743,10 +1749,12 @@ mpt3sas_scsih_scsi_lookup_get(struct MPT3SAS_ADAPTER *ioc, u16 smid)
 	struct scsi_cmnd *scmd = NULL;
 	struct scsiio_tracker *st;
 	Mpi25SCSIIORequest_t *mpi_request;
+	u16 tag = smid - 1;
 
 	if (smid > 0  &&
 	    smid <= ioc->scsiio_depth - INTERNAL_SCSIIO_CMDS_COUNT) {
-		u32 unique_tag = smid - 1;
+		u32 unique_tag =
+		    ioc->io_queue_num[tag] << BLK_MQ_UNIQUE_TAG_BITS | tag;
 
 		mpi_request = mpt3sas_base_get_msg_frame(ioc, smid);
 
@@ -11599,6 +11607,22 @@ scsih_scan_finished(struct Scsi_Host *shost, unsigned long time)
 	return 1;
 }
 
+/**
+ * scsih_map_queues - map reply queues with request queues
+ * @shost: SCSI host pointer
+ */
+static int scsih_map_queues(struct Scsi_Host *shost)
+{
+	struct MPT3SAS_ADAPTER *ioc =
+	    (struct MPT3SAS_ADAPTER *)shost->hostdata;
+
+	if (ioc->shost->nr_hw_queues == 1)
+		return 0;
+
+	return blk_mq_pci_map_queues(&shost->tag_set.map[HCTX_TYPE_DEFAULT],
+	    ioc->pdev, ioc->high_iops_queues);
+}
+
 /* shost template for SAS 2.0 HBA devices */
 static struct scsi_host_template mpt2sas_driver_template = {
 	.module				= THIS_MODULE,
@@ -11666,6 +11690,7 @@ static struct scsi_host_template mpt3sas_driver_template = {
 	.sdev_attrs			= mpt3sas_dev_attrs,
 	.track_queue_depth		= 1,
 	.cmd_size			= sizeof(struct scsiio_tracker),
+	.map_queues			= scsih_map_queues,
 };
 
 /* raid transport support for SAS 3.0 HBA devices */
@@ -12028,6 +12053,21 @@ _scsih_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	} else
 		ioc->hide_drives = 0;
 
+	shost->host_tagset = 0;
+	shost->nr_hw_queues = 1;
+
+	if (ioc->is_gen35_ioc && ioc->reply_queue_count > 1 &&
+	    host_tagset_enable && ioc->smp_affinity_enable) {
+
+		shost->host_tagset = 1;
+		shost->nr_hw_queues =
+		    ioc->reply_queue_count - ioc->high_iops_queues;
+
+		dev_info(&ioc->pdev->dev,
+		    "Max SCSIIO MPT commands: %d shared with nr_hw_queues = %d\n",
+		    shost->can_queue, shost->nr_hw_queues);
+	}
+
 	rv = scsi_add_host(shost, &pdev->dev);
 	if (rv) {
 		ioc_err(ioc, "failure at %s:%d/%s()!\n",