Michael S. Tsirkin wrote:
This implements optional MSI-X support in virtio_pci. MSI-X is used whenever the host supports at least 2 MSI-X vectors: 1 for configuration changes and 1 for virtqueues. Per-virtqueue vectors are allocated if enough vectors available. +static int vp_request_vectors(struct virtio_device *vdev, unsigned max_vqs) +{ + struct virtio_pci_device *vp_dev = to_vp_device(vdev); + const char *name = dev_name(&vp_dev->vdev.dev); + unsigned i, v; + int err = -ENOMEM; + /* We want at most one vector per queue and one for config changes. + * Fallback to separate vectors for config and a shared for queues. + * Finally fall back to regular interrupts. */ + int options[] = { max_vqs + 1, 2 }; + int nvectors = max(options[0], options[1]); + + vp_dev->msix_entries = kmalloc(nvectors * sizeof *vp_dev->msix_entries, + GFP_KERNEL); + if (!vp_dev->msix_entries) + goto error_entries; + vp_dev->msix_names = kmalloc(nvectors * sizeof *vp_dev->msix_names, + GFP_KERNEL); + if (!vp_dev->msix_names) + goto error_names; + + for (i = 0; i < nvectors; ++i) + vp_dev->msix_entries[i].entry = i; + + err = vp_enable_msix(vp_dev->pci_dev, vp_dev->msix_entries, + options, ARRAY_SIZE(options)); + if (err < 0) { + /* Can't allocate enough MSI-X vectors, use regular interrupt */ + vp_dev->msix_vectors = 0; + err = request_irq(vp_dev->pci_dev->irq, vp_interrupt, + IRQF_SHARED, name, vp_dev); + if (err) + goto error_irq; + vp_dev->intx_enabled = 1; + } else { + vp_dev->msix_vectors = err; + vp_dev->msix_enabled = 1; + + /* Set the vector used for configuration */ + v = vp_dev->msix_used_vectors; + snprintf(vp_dev->msix_names[v], sizeof *vp_dev->msix_names, + "%s-config", name); + err = request_irq(vp_dev->msix_entries[v].vector, + vp_config_changed, 0, vp_dev->msix_names[v], + vp_dev); + if (err) + goto error_irq; + ++vp_dev->msix_used_vectors; + + iowrite16(v, vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR); + /* Verify we had enough resources to assign the vector */ + v = ioread16(vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR); + if (v == VIRTIO_MSI_NO_VECTOR) { + err = -EBUSY; + goto error_irq; + } + } + + if (vp_dev->msix_vectors && vp_dev->msix_vectors != max_vqs + 1) { + /* Shared vector for all VQs */ + v = vp_dev->msix_used_vectors; + snprintf(vp_dev->msix_names[v], sizeof *vp_dev->msix_names, + "%s-virtqueues", name); + err = request_irq(vp_dev->msix_entries[v].vector, + vp_vring_interrupt, 0, vp_dev->msix_names[v], + vp_dev); + if (err) + goto error_irq; + ++vp_dev->msix_used_vectors; + } + return 0; +error_irq: + vp_free_vectors(vdev); + kfree(vp_dev->msix_names); +error_names: + kfree(vp_dev->msix_entries); +error_entries: + return err; +} + @@ -272,12 +412,43 @@ static struct virtqueue *vp_find_vq(struct virtio_device *vdev, unsigned index, vq->priv = info; info->vq = vq;+ /* allocate per-vq vector if available and necessary */+ if (callback && vp_dev->msix_used_vectors < vp_dev->msix_vectors) { + vector = vp_dev->msix_used_vectors; + snprintf(vp_dev->msix_names[vector], sizeof *vp_dev->msix_names, + "%s-%s", dev_name(&vp_dev->vdev.dev), name); + err = request_irq(vp_dev->msix_entries[vector].vector, + vring_interrupt, 0, + vp_dev->msix_names[vector], vq); + if (err) + goto out_request_irq; + info->vector = vector; + ++vp_dev->msix_used_vectors; + } else + vector = VP_MSIX_VQ_VECTOR; + + if (callback && vp_dev->msix_enabled) { + iowrite16(vector, vp_dev->ioaddr + VIRTIO_MSI_QUEUE_VECTOR); + vector = ioread16(vp_dev->ioaddr + VIRTIO_MSI_QUEUE_VECTOR); + if (vector == VIRTIO_MSI_NO_VECTOR) { + err = -EBUSY; + goto out_assign; + } + } +
I'm not sure I understand how the vq -> msi mapping works. Do we actually support an arbitrary mapping, or just either linear or n:1?
I don't mind the driver being limited, but the device interface should be flexible. We'll want to deal with limited vector availability soon.
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