[PATCH v2] vp_vdpa: fix the method of calculating vectors

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From: Yuxue Liu <yuxue.liu@xxxxxxxxxxxxxxx>

When there is a ctlq and it doesn't require interrupt
callbacks,the original method of calculating vectors
wastes hardware MSI or MSI-X resources as well as system
IRQ resources. Referencing the per_vq_vectors mode in the
vp_find_vqs_msix function, calculate the required number
of vectors based on whether the callback is set.

Signed-off-by: Yuxue Liu <yuxue.liu@xxxxxxxxxxxxxxx>
---

V1 -> V2: fix when allocating IRQs, scan all queues.
V1: https://lore.kernel.org/all/20240318030121.1873-1-gavin.liu@xxxxxxxxxxxxxxx/
---
 drivers/vdpa/virtio_pci/vp_vdpa.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/drivers/vdpa/virtio_pci/vp_vdpa.c b/drivers/vdpa/virtio_pci/vp_vdpa.c
index 281287fae89f..87329d4358ce 100644
--- a/drivers/vdpa/virtio_pci/vp_vdpa.c
+++ b/drivers/vdpa/virtio_pci/vp_vdpa.c
@@ -160,8 +160,15 @@ static int vp_vdpa_request_irq(struct vp_vdpa *vp_vdpa)
 	struct pci_dev *pdev = mdev->pci_dev;
 	int i, ret, irq;
 	int queues = vp_vdpa->queues;
-	int vectors = queues + 1;
+	int allocated_vectors, vectors = 0;
+	u16 msix_vec;
 
+	for (i = 0; i < queues; i++) {
+		if (vp_vdpa->vring[i].cb.callback != NULL)
+			vectors++;
+	}
+	/*By default, config interrupts request a single vector*/
+	vectors = vectors + 1;
 	ret = pci_alloc_irq_vectors(pdev, vectors, vectors, PCI_IRQ_MSIX);
 	if (ret != vectors) {
 		dev_err(&pdev->dev,
@@ -169,13 +176,17 @@ static int vp_vdpa_request_irq(struct vp_vdpa *vp_vdpa)
 			vectors, ret);
 		return ret;
 	}
-
 	vp_vdpa->vectors = vectors;
 
 	for (i = 0; i < queues; i++) {
+		if (vp_vdpa->vring[i].cb.callback == NULL)
+			continue;
+		else
+			msix_vec = allocated_vectors++;
+
 		snprintf(vp_vdpa->vring[i].msix_name, VP_VDPA_NAME_SIZE,
 			"vp-vdpa[%s]-%d\n", pci_name(pdev), i);
-		irq = pci_irq_vector(pdev, i);
+		irq = pci_irq_vector(pdev, msix_vec);
 		ret = devm_request_irq(&pdev->dev, irq,
 				       vp_vdpa_vq_handler,
 				       0, vp_vdpa->vring[i].msix_name,
@@ -185,13 +196,14 @@ static int vp_vdpa_request_irq(struct vp_vdpa *vp_vdpa)
 				"vp_vdpa: fail to request irq for vq %d\n", i);
 			goto err;
 		}
-		vp_modern_queue_vector(mdev, i, i);
+		vp_modern_queue_vector(mdev, i, msix_vec);
 		vp_vdpa->vring[i].irq = irq;
 	}
 
+	msix_vec = allocated_vectors;
 	snprintf(vp_vdpa->msix_name, VP_VDPA_NAME_SIZE, "vp-vdpa[%s]-config\n",
 		 pci_name(pdev));
-	irq = pci_irq_vector(pdev, queues);
+	irq = pci_irq_vector(pdev, msix_vec);
 	ret = devm_request_irq(&pdev->dev, irq,	vp_vdpa_config_handler, 0,
 			       vp_vdpa->msix_name, vp_vdpa);
 	if (ret) {
@@ -199,7 +211,7 @@ static int vp_vdpa_request_irq(struct vp_vdpa *vp_vdpa)
 			"vp_vdpa: fail to request irq for vq %d\n", i);
 			goto err;
 	}
-	vp_modern_config_vector(mdev, queues);
+	vp_modern_config_vector(mdev, msix_vec);
 	vp_vdpa->config_irq = irq;
 
 	return 0;
-- 
2.43.0





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