[PATCH 4/9] virtio_pci: simplify MSI-X setup

Christoph Hellwig
2017-02-05T17:15:46Z

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>
---
drivers/virtio/virtio_pci_common.c | 35 ++++++++++++++++++-----------------
1 file changed, 18 insertions(+), 17 deletions(-)

diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index b83053082875..822f8e5dcee4 100644
--- 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);
}

--
2.11.0