Revert "virtio_pci: simplify MSI-X setup"

This reverts commit 52a6151.

Conflicts:
	drivers/virtio/virtio_pci_common.c

The cleanup seems to be one of the changes that broke
hybernation for some users. We are still not sure why
but revert helps.

This reverts the cleanup changes but keeps the affinity support.

Tested-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/virtio/virtio_pci_common.c

@@ -143,13 +143,13 @@ void vp_del_vqs(struct virtio_device *vdev)
 
 static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned nvqs,
 		struct virtqueue *vqs[], vq_callback_t *callbacks[],
-		const char * const names[], struct irq_affinity *desc)
+		const char * const names[], bool per_vq_vectors,
+		struct irq_affinity *desc)
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
 	const char *name = dev_name(&vp_dev->vdev.dev);
 	int i, err = -ENOMEM, allocated_vectors, nvectors;
 	unsigned flags = PCI_IRQ_MSIX;
-	bool shared = false;
 	u16 msix_vec;
 
 	if (desc) {
@@ -162,16 +162,12 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned nvqs,
 		if (callbacks[i])
 			nvectors++;
 
-	/* Try one vector per queue first. */
-	err = pci_alloc_irq_vectors_affinity(vp_dev->pci_dev, nvectors,
-			nvectors, flags, desc);
-	if (err < 0) {
-		/* Fallback to one vector for config, one shared for queues. */
-		shared = true;
+	if (per_vq_vectors) {
+		err = pci_alloc_irq_vectors_affinity(vp_dev->pci_dev, nvectors,
+				nvectors, flags, desc);
+	} else {
 		err = pci_alloc_irq_vectors(vp_dev->pci_dev, 2, 2,
 				PCI_IRQ_MSIX);
-		if (err < 0)
-			return err;
 	}
 	if (err < 0)
 		return err;
@@ -199,7 +195,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned nvqs,
 	err = request_irq(pci_irq_vector(vp_dev->pci_dev, 0), vp_config_changed,
 			0, vp_dev->msix_names[0], vp_dev);
 	if (err)
-		goto out_free_msix_affinity_masks;
+		goto out_free_irq_vectors;
 
 	/* Verify we had enough resources to assign the vector */
 	if (vp_dev->config_vector(vp_dev, 0) == VIRTIO_MSI_NO_VECTOR) {
@@ -249,11 +245,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned nvqs,
 		}
 		vp_dev->msix_vector_map[i] = msix_vec;
 
-		/*
-		 * Use a different vector for each queue if they are available,
-		 * else share the same vector for all VQs.
-		 */
-		if (!shared)
+		if (per_vq_vectors)
 			allocated_vectors++;
 	}
 
@@ -319,9 +311,15 @@ int vp_find_vqs(struct virtio_device *vdev, unsigned nvqs,
 {
 	int err;
 
-	err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names, desc);
+	/* Try MSI-X with one vector per queue. */
+	err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names, true, desc);
+	if (!err)
+		return 0;
+	/* Fallback: MSI-X with one vector for config, one shared for queues. */
+	err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names, false, desc);
 	if (!err)
 		return 0;
+	/* Finally fall back to regular interrupts. */
 	return vp_find_vqs_intx(vdev, nvqs, vqs, callbacks, names);
 }