[PATCH V4 2/4] vDPA/ifcvf: implement device MSIX vector allocator

[Zhu Lingshan <lingshan.zhu@intel.com>]

This commit implements a MSIX vector allocation helper
for vqs and config interrupts.

Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
---
 drivers/vdpa/ifcvf/ifcvf_main.c | 35 +++++++++++++++++++++++++++++++--
 1 file changed, 33 insertions(+), 2 deletions(-)

diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c b/drivers/vdpa/ifcvf/ifcvf_main.c
index d1a6b5ab543c..44c89ab0b6da 100644
--- a/drivers/vdpa/ifcvf/ifcvf_main.c
+++ b/drivers/vdpa/ifcvf/ifcvf_main.c
@@ -58,14 +58,45 @@ static void ifcvf_free_irq(struct ifcvf_adapter *adapter, int queues)
 	ifcvf_free_irq_vectors(pdev);
 }
 
+/* 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 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);
+
+	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, i, ret, irq;
+	int vector, nvectors, i, ret, irq;
 	u16 max_intr;
 
-	/* all queues and config interrupt  */
+	nvectors = ifcvf_alloc_vectors(adapter);
+	if (!(nvectors > 0))
+		return nvectors;
+
 	max_intr = vf->nr_vring + 1;
 
 	ret = pci_alloc_irq_vectors(pdev, max_intr,
-- 
2.27.0