scsi: lpfc: Fix crash when cpu count is 1 and null irq affinity mask

When a configurations runs with a single cpu (such as a kdump kernel),
which causes the driver to request a single vector, when the driver
subsequently requests an irq affinity mask, the mask comes back null.  The
driver currently does nothing in this scenario, which leaves mappings to
hardware queues incomplete and crashes the system.

Fix by recognizing the null mask and assigning the vector to the first cpu
in the system.
Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/lpfc/lpfc_init.c

@@ -10776,12 +10776,31 @@ lpfc_cpu_affinity_check(struct lpfc_hba *phba, int vectors)
 	/* This loop sets up all CPUs that are affinitized with a
 	 * irq vector assigned to the driver. All affinitized CPUs
 	 * will get a link to that vectors IRQ and EQ.
+	 *
+	 * NULL affinity mask handling:
+	 * If irq count is greater than one, log an error message.
+	 * If the null mask is received for the first irq, find the
+	 * first present cpu, and assign the eq index to ensure at
+	 * least one EQ is assigned.
 	 */
 	for (idx = 0; idx <  phba->cfg_irq_chann; idx++) {
 		/* Get a CPU mask for all CPUs affinitized to this vector */
 		maskp = pci_irq_get_affinity(phba->pcidev, idx);
-		if (!maskp)
-			continue;
+		if (!maskp) {
+			if (phba->cfg_irq_chann > 1)
+				lpfc_printf_log(phba, KERN_ERR, LOG_INIT,
+						"3329 No affinity mask found "
+						"for vector %d (%d)\n",
+						idx, phba->cfg_irq_chann);
+			if (!idx) {
+				cpu = cpumask_first(cpu_present_mask);
+				cpup = &phba->sli4_hba.cpu_map[cpu];
+				cpup->eq = idx;
+				cpup->irq = pci_irq_vector(phba->pcidev, idx);
+				cpup->flag |= LPFC_CPU_FIRST_IRQ;
+			}
+			break;
+		}
 
 		i = 0;
 		/* Loop through all CPUs associated with vector idx */