virtio_pci: simplify MSI-X setup

Try to grab the MSI-X vectors early and fall back to the shared one
before doing lots of allocations.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index b83053082875bf0f4941e9de7c6cbcfba9258d58..822f8e5dcee421122f5cf7e21982b60790bce69e 100644 (file)
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -142,14 +142,13 @@ 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[],
-                             bool per_vq_vectors)
+               struct virtqueue *vqs[], vq_callback_t *callbacks[],
+               const char * const names[])
 {
        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;
+       bool shared = false;
        u16 msix_vec;
 
        nvectors = 1;
@@ -157,12 +156,16 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned nvqs,
                if (callbacks[i])
                        nvectors++;
 
-       if (per_vq_vectors) {
-               err = pci_alloc_irq_vectors(vp_dev->pci_dev, nvectors, nvectors,
-                               PCI_IRQ_MSIX);
-       } else {
+       /* Try one vector per queue first. */
+       err = pci_alloc_irq_vectors(vp_dev->pci_dev, nvectors, nvectors,
+                       PCI_IRQ_MSIX);
+       if (err < 0) {
+               /* Fallback to one vector for config, one shared for queues. */
+               shared = true;
                err = pci_alloc_irq_vectors(vp_dev->pci_dev, 2, 2,
                                PCI_IRQ_MSIX);
+               if (err < 0)
+                       return err;
        }
        if (err < 0)
                return err;
@@ -190,7 +193,7 @@ 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_irq_vectors;
+               goto out_free_msix_affinity_masks;
 
        /* Verify we had enough resources to assign the vector */
        if (vp_dev->config_vector(vp_dev, 0) == VIRTIO_MSI_NO_VECTOR) {
@@ -240,7 +243,11 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned nvqs,
                }
                vp_dev->msix_vector_map[i] = msix_vec;
 
-               if (per_vq_vectors)
+               /*
+                * Use a different vector for each queue if they are available,
+                * else share the same vector for all VQs.
+                */
+               if (!shared)
                        allocated_vectors++;
        }
 
@@ -307,15 +314,9 @@ int vp_find_vqs(struct virtio_device *vdev, unsigned nvqs,
 {
        int err;
 
-       /* Try MSI-X with one vector per queue. */
-       err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names, true);
-       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);
+       err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names);
        if (!err)
                return 0;
-       /* Finally fall back to regular interrupts. */
        return vp_find_vqs_intx(vdev, nvqs, vqs, callbacks, names);
 }