vDPA/ifcvf: implement device MSIX vector allocator

This commit implements a MSIX vector allocation helper
for vqs and config interrupts.
Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Link: https://lore.kernel.org/r/20220222115428.998334-4-lingshan.zhu@intel.comSigned-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/ifcvf/ifcvf_main.c

@@ -58,23 +58,44 @@ static void ifcvf_free_irq(struct ifcvf_adapter *adapter, int queues)
 	ifcvf_free_irq_vectors(pdev);
 }
 
-static int ifcvf_request_irq(struct ifcvf_adapter *adapter)
+/* ifcvf MSIX vectors allocator, this helper tries to allocate
+ * vectors for all virtqueues and the config interrupt.
+ * It returns the number of allocated vectors, negative
+ * return value when fails.
+ */
+static int ifcvf_alloc_vectors(struct ifcvf_adapter *adapter)
 {
 	struct pci_dev *pdev = adapter->pdev;
 	struct ifcvf_hw *vf = &adapter->vf;
-	int vector, i, ret, irq;
-	u16 max_intr;
+	int max_intr, ret;
 
 	/* all queues and config interrupt  */
 	max_intr = vf->nr_vring + 1;
+	ret = pci_alloc_irq_vectors(pdev, 1, max_intr, PCI_IRQ_MSIX | PCI_IRQ_AFFINITY);
 
-	ret = pci_alloc_irq_vectors(pdev, max_intr,
-				    max_intr, PCI_IRQ_MSIX);
 	if (ret < 0) {
 		IFCVF_ERR(pdev, "Failed to alloc IRQ vectors\n");
 		return ret;
 	}
 
+	if (ret < max_intr)
+		IFCVF_INFO(pdev,
+			   "Requested %u vectors, however only %u allocated, lower performance\n",
+			   max_intr, ret);
+
+	return ret;
+}
+
+static int ifcvf_request_irq(struct ifcvf_adapter *adapter)
+{
+	struct pci_dev *pdev = adapter->pdev;
+	struct ifcvf_hw *vf = &adapter->vf;
+	int vector, nvectors, i, ret, irq;
+
+	nvectors = ifcvf_alloc_vectors(adapter);
+	if (nvectors <= 0)
+		return -EFAULT;
+
 	snprintf(vf->config_msix_name, 256, "ifcvf[%s]-config\n",
 		 pci_name(pdev));
 	vector = 0;