FAILED: patch "[PATCH] scsi: qla2xxx: Use correct number of vectors for online CPUs" failed to apply to 4.20-stable tree

The patch below does not apply to the 4.20-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f0783d43dde4bb349fcd667df0afabbdbab8b477 Mon Sep 17 00:00:00 2001
From: Ming Lei <[email protected]>
Date: Fri, 11 Jan 2019 09:40:47 -0800
Subject: [PATCH] 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().

index 26b93c563f92..d1fc4958222a 100644
@@ -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 {

index 30d3090842f8..8507c43b918c 100644
@@ -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);

index ea69dafc9774..c6ef83d0d99b 100644
@@ -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;
 }