diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
index accd16082348..102f5c5fcfe0 100644
--- a/drivers/pci/pcie/portdrv_core.c
+++ b/drivers/pci/pcie/portdrv_core.c
@@ -43,6 +43,53 @@ static void release_pcie_device(struct device *dev)
 	kfree(to_pcie_device(dev));
 }
 
+/*
+ * Fill in *pme, *aer, *dpc with the relevant Interrupt Message Numbers if
+ * services are enabled in "mask".  Return the number of MSI/MSI-X vectors
+ * required to accommodate the largest Message Number.
+ */
+static int pcie_message_numbers(struct pci_dev *dev, int mask,
+				u32 *pme, u32 *aer, u32 *dpc)
+{
+	u32 nvec = 0, pos, reg32;
+	u16 reg16;
+
+	/*
+	 * The Interrupt Message Number indicates which vector is used, i.e.,
+	 * the MSI-X table entry or the MSI offset between the base Message
+	 * Data and the generated interrupt message.  See PCIe r3.1, sec
+	 * 7.8.2, 7.10.10, 7.31.2.
+	 */
+
+	if (mask & (PCIE_PORT_SERVICE_PME | PCIE_PORT_SERVICE_HP)) {
+		pcie_capability_read_word(dev, PCI_EXP_FLAGS, &reg16);
+		*pme = (reg16 & PCI_EXP_FLAGS_IRQ) >> 9;
+		nvec = *pme + 1;
+	}
+
+	if (mask & PCIE_PORT_SERVICE_AER) {
+		pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR);
+		if (pos) {
+			pci_read_config_dword(dev, pos + PCI_ERR_ROOT_STATUS,
+					      &reg32);
+			*aer = (reg32 & PCI_ERR_ROOT_AER_IRQ) >> 27;
+			nvec = max(nvec, *aer + 1);
+		}
+	}
+
+	if (mask & PCIE_PORT_SERVICE_DPC) {
+		pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DPC);
+		if (pos) {
+			pci_read_config_word(dev, pos + PCI_EXP_DPC_CAP,
+					     &reg16);
+			*dpc = reg16 & PCI_EXP_DPC_IRQ;
+			nvec = max(nvec, *dpc + 1);
+		}
+	}
+
+	return nvec;
+}
+
 /**
  * pcie_port_enable_irq_vec - try to set up MSI-X or MSI as interrupt mode
  * for given port
@@ -54,7 +101,8 @@ static void release_pcie_device(struct device *dev)
  */
 static int pcie_port_enable_irq_vec(struct pci_dev *dev, int *irqs, int mask)
 {
-	int nr_entries, entry, nvec = 0;
+	int nr_entries, nvec;
+	u32 pme = 0, aer = 0, dpc = 0;
 
 	/* Allocate the maximum possible number of MSI/MSI-X vectors */
 	nr_entries = pci_alloc_irq_vectors(dev, 1, PCIE_PORT_MAX_MSI_ENTRIES,
@@ -62,54 +110,24 @@ static int pcie_port_enable_irq_vec(struct pci_dev *dev, int *irqs, int mask)
 	if (nr_entries < 0)
 		return nr_entries;
 
-	/*
-	 * The Interrupt Message Number indicates which vector is used, i.e.,
-	 * the MSI-X table entry or the MSI offset between the base Message
-	 * Data and the generated interrupt message.  See PCIe r3.1, sec
-	 * 7.8.2, 7.10.10, 7.31.2.
-	 */
-	if (mask & (PCIE_PORT_SERVICE_PME | PCIE_PORT_SERVICE_HP)) {
-		u16 reg16;
-
-		pcie_capability_read_word(dev, PCI_EXP_FLAGS, &reg16);
-		entry = (reg16 & PCI_EXP_FLAGS_IRQ) >> 9;
-		if (entry >= nr_entries)
-			goto out_free_irqs;
-
-		/* PME and hotplug share an MSI/MSI-X vector */
-		irqs[PCIE_PORT_SERVICE_PME_SHIFT] = pci_irq_vector(dev, entry);
-		irqs[PCIE_PORT_SERVICE_HP_SHIFT] = pci_irq_vector(dev, entry);
-
-		nvec = max(nvec, entry + 1);
+	/* See how many and which Interrupt Message Numbers we actually use */
+	nvec = pcie_message_numbers(dev, mask, &pme, &aer, &dpc);
+	if (nvec > nr_entries) {
+		pci_free_irq_vectors(dev);
+		return -EIO;
 	}
 
-	if (mask & PCIE_PORT_SERVICE_AER) {
-		u32 reg32, pos;
-
-		pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR);
-		pci_read_config_dword(dev, pos + PCI_ERR_ROOT_STATUS, &reg32);
-		entry = (reg32 & PCI_ERR_ROOT_AER_IRQ) >> 27;
-		if (entry >= nr_entries)
-			goto out_free_irqs;
-
-		irqs[PCIE_PORT_SERVICE_AER_SHIFT] = pci_irq_vector(dev, entry);
-
-		nvec = max(nvec, entry + 1);
+	/* PME and hotplug share an MSI/MSI-X vector */
+	if (mask & (PCIE_PORT_SERVICE_PME | PCIE_PORT_SERVICE_HP)) {
+		irqs[PCIE_PORT_SERVICE_PME_SHIFT] = pci_irq_vector(dev, pme);
+		irqs[PCIE_PORT_SERVICE_HP_SHIFT] = pci_irq_vector(dev, pme);
 	}
 
-	if (mask & PCIE_PORT_SERVICE_DPC) {
-		u16 reg16, pos;
-
-		pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DPC);
-		pci_read_config_word(dev, pos + PCI_EXP_DPC_CAP, &reg16);
-		entry = reg16 & PCI_EXP_DPC_IRQ;
-		if (entry >= nr_entries)
-			goto out_free_irqs;
-
-		irqs[PCIE_PORT_SERVICE_DPC_SHIFT] = pci_irq_vector(dev, entry);
+	if (mask & PCIE_PORT_SERVICE_AER)
+		irqs[PCIE_PORT_SERVICE_AER_SHIFT] = pci_irq_vector(dev, aer);
 
-		nvec = max(nvec, entry + 1);
-	}
+	if (mask & PCIE_PORT_SERVICE_DPC)
+		irqs[PCIE_PORT_SERVICE_DPC_SHIFT] = pci_irq_vector(dev, dpc);
 
 	/* If we allocated more than we need, free them and allocate fewer */
 	if (nvec != nr_entries) {
@@ -122,10 +140,6 @@ static int pcie_port_enable_irq_vec(struct pci_dev *dev, int *irqs, int mask)
 	}
 
 	return 0;
-
-out_free_irqs:
-	pci_free_irq_vectors(dev);
-	return -EIO;
 }
 
 /**
