A virtqueue is a coherent DMA mapping. Use the DMA API for it. This fixes virtio_pci on Xen.
As an optimization, this only enables asks virtio_ring to use the DMA API if !PCI_DMA_BUS_IS_PHYS. Eventually, once the DMA API is known to be efficient on all relevant architectures, this optimization can be removed. Signed-off-by: Andy Lutomirski <[email protected]> --- drivers/virtio/virtio_pci.c | 40 +++++++++++++++++++++++++++++++--------- 1 file changed, 31 insertions(+), 9 deletions(-) diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c index a1f299fa4626..226b46b08727 100644 --- a/drivers/virtio/virtio_pci.c +++ b/drivers/virtio/virtio_pci.c @@ -80,8 +80,9 @@ struct virtio_pci_vq_info /* the number of entries in the queue */ int num; - /* the virtual address of the ring queue */ - void *queue; + /* the ring queue */ + void *queue; /* virtual address */ + dma_addr_t queue_dma_addr; /* bus address */ /* the list node for the virtqueues list */ struct list_head node; @@ -417,20 +418,32 @@ static struct virtqueue *setup_vq(struct virtio_device *vdev, unsigned index, info->num = num; info->msix_vector = msix_vec; - size = PAGE_ALIGN(vring_size(num, VIRTIO_PCI_VRING_ALIGN)); - info->queue = alloc_pages_exact(size, GFP_KERNEL|__GFP_ZERO); + size = vring_size(num, VIRTIO_PCI_VRING_ALIGN); + info->queue = dma_zalloc_coherent(vdev->dev.parent, size, + &info->queue_dma_addr, GFP_KERNEL); if (info->queue == NULL) { err = -ENOMEM; goto out_info; } /* activate the queue */ - iowrite32(virt_to_phys(info->queue) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT, + iowrite32(info->queue_dma_addr >> VIRTIO_PCI_QUEUE_ADDR_SHIFT, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN); - /* create the vring */ + /* + * Create the vring. If there is an IOMMU of any sort, including + * Xen paravirt's ersatz IOMMU, use it. If the host wants physical + * addresses instead of bus addresses, the host shouldn't expose + * an IOMMU. + * + * As an optimization, if the platform promises to have physical + * PCI DMA, we turn off DMA mapping in virtio_ring. If the + * platform's DMA API implementation is well optimized, this + * should have almost no effect, but that's a dangerous thing to + * rely on. + */ vq = vring_new_virtqueue(index, info->num, VIRTIO_PCI_VRING_ALIGN, vdev, - true, false, info->queue, + true, !PCI_DMA_BUS_IS_PHYS, info->queue, vp_notify, callback, name); if (!vq) { err = -ENOMEM; @@ -463,7 +476,8 @@ out_assign: vring_del_virtqueue(vq); out_activate_queue: iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN); - free_pages_exact(info->queue, size); + dma_free_coherent(vdev->dev.parent, size, + info->queue, info->queue_dma_addr); out_info: kfree(info); return ERR_PTR(err); @@ -494,7 +508,8 @@ static void vp_del_vq(struct virtqueue *vq) iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN); size = PAGE_ALIGN(vring_size(info->num, VIRTIO_PCI_VRING_ALIGN)); - free_pages_exact(info->queue, size); + dma_free_coherent(vq->vdev->dev.parent, size, + info->queue, info->queue_dma_addr); kfree(info); } @@ -713,6 +728,13 @@ static int virtio_pci_probe(struct pci_dev *pci_dev, if (err) goto out; + err = dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(64)); + if (err) + err = dma_set_mask_and_coherent(&pci_dev->dev, + DMA_BIT_MASK(32)); + if (err) + dev_warn(&pci_dev->dev, "Failed to enable 64-bit or 32-bit DMA. Trying to continue, but this might not work.\n"); + err = pci_request_regions(pci_dev, "virtio-pci"); if (err) goto out_enable_device; -- 1.9.3 _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
