scsi: qla2xxx: Use correct number of vectors for online CPUs

When SCSI-MQ is enabled, in some case system would present
nr_possible_cpus() which is greater than requested vectors by the
driver. This results into driver being able to get larger number of MSI-X
vectors than actual online CPUs.  Driver then uses
pci_alloc_irq_vectors_affinity() to assign 1:1 mapping and affinity for
each MSI-x vector to CPUs. When the command is submitted using MSI-x
vector, assigned to offline CPU, it results in an ABTS and system
hang. This hang is result of a driver not being able to process interrupt
on a vector assigned to an Off-line CPUs

This patch fixes this issue by setting irq_offset value for the
blk_mq_pci_map_queues() to use only those CPUs which has CPU mask affinity
assigned and are online. By using the irq_offset value, driver will allow
online cpumask to decide which vectors are used in blk_mq_pci_map_queues().

Fixes: 5601236 ("scsi: qla2xxx: Add Block Multi Queue functionality.")
Cc: <stable@vger.kernel.org> #4.19
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Himanshu Madhani <hmadhani@marvell.com>
Tested-by: Himanshu Madhani <hmadhani@marvell.com>
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Author: Ming Lei

drivers/scsi/qla2xxx/qla_def.h

@@ -4394,6 +4394,8 @@ typedef struct scsi_qla_host {
 	uint16_t	n2n_id;
 	struct list_head gpnid_list;
 	struct fab_scan scan;
+
+	unsigned int irq_offset;
 } scsi_qla_host_t;
 
 struct qla27xx_image_status {

drivers/scsi/qla2xxx/qla_isr.c

@@ -3446,6 +3446,7 @@ qla24xx_enable_msix(struct qla_hw_data *ha, struct rsp_que *rsp)
 			    "Adjusted Max no of queues pairs: %d.\n", ha->max_qpairs);
 		}
 	}
+	vha->irq_offset = desc.pre_vectors;
 	ha->msix_entries = kcalloc(ha->msix_count,
 				   sizeof(struct qla_msix_entry),
 				   GFP_KERNEL);

drivers/scsi/qla2xxx/qla_os.c

@@ -6939,7 +6939,7 @@ static int qla2xxx_map_queues(struct Scsi_Host *shost)
 	if (USER_CTRL_IRQ(vha->hw))
 		rc = blk_mq_map_queues(qmap);
 	else
-		rc = blk_mq_pci_map_queues(qmap, vha->hw->pdev, 0);
+		rc = blk_mq_pci_map_queues(qmap, vha->hw->pdev, vha->irq_offset);
 	return rc;
 }