On Tue, Aug 26, 2014 at 02:17:02PM -0700, Andy Lutomirski wrote:
> A virtqueue is a coherent DMA mapping. Use the DMA API for it.
> This fixes virtio_pci on Xen.
>
> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> ---
> drivers/virtio/virtio_pci.c | 25 ++++++++++++++++++-------
> 1 file changed, 18 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
> index 3d1463c6b120..19039c5bec24 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;
> @@ -417,15 +418,16 @@ 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 */
> @@ -462,7 +464,8 @@ 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);
> @@ -493,7 +496,8 @@ 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);
> }
>
> @@ -712,6 +716,13 @@ static int virtio_pci_probe(struct pci_dev *pci_dev,
> if (err)
> goto out;
>
> + /*
> + * We support 64-bit DMA. If this fails (e.g. some bridge
> + * or PV code doesn't or DAC is disabled), then we're okay
> + * with 32-bit DMA.
<scratches his head>
I am having a hard time parsing that. Could you expand a bit the
faulting use-case please?
> + */
> + dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(64));
The usual process is:
ret = dma_set_mask_and_coherent(..)
if (ret)
ret = dma_set_mask_and_coherent(.., DMA_BIT_MASK(32))
if (ret)
pr_warn("We are truly screwed. Good luck!\n");
> +
> err = pci_request_regions(pci_dev, "virtio-pci");
> if (err)
> goto out_enable_device;
> --
> 1.9.3
>
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