Re: [PATCH v13 09/15] vfio/type1: vfio_find_dma accepting a type argument

Alex Williamson
2016-10-06T20:18:49Z

On Thu, 6 Oct 2016 08:45:25 +0000
Eric Auger <eric.auger-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:

> In our RB-tree we get prepared to insert slots of different types
> (USER and RESERVED). It becomes useful to be able to search for dma
> slots of a specific type or any type.
>
> This patch introduces vfio_find_dma_from_node which starts the
> search from a given node and stops on the first node that matches
> the @start and @size parameters. If this node also matches the
> @type parameter, the node is returned else NULL is returned.
>
> At the moment we only have USER SLOTS so the type will always match.
>
> In a separate patch, this function will be enhanced to pursue the
> search recursively in case a node with a different type is
> encountered.
>
> Signed-off-by: Eric Auger <eric.auger-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> ---
> drivers/vfio/vfio_iommu_type1.c | 53 +++++++++++++++++++++++++++++++++--------
> 1 file changed, 43 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index a9f8b93..cb7267a 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -94,25 +94,56 @@ struct vfio_group {
> * into DMA'ble space using the IOMMU
> */
>
> -static struct vfio_dma *vfio_find_dma(struct vfio_iommu *iommu,
> - dma_addr_t start, size_t size)
> +/**
> + * vfio_find_dma_from_node: looks for a dma slot intersecting a window
> + * from a given rb tree node
> + * @top: top rb tree node where the search starts (including this node)
> + * @start: window start
> + * @size: window size
> + * @type: window type
> + */
> +static struct vfio_dma *vfio_find_dma_from_node(struct rb_node *top,
> + dma_addr_t start, size_t size,
> + enum vfio_iova_type type)
> {
> - struct rb_node *node = iommu->dma_list.rb_node;
> + struct rb_node *node = top;
> + struct vfio_dma *dma;
>
> while (node) {
> - struct vfio_dma *dma = rb_entry(node, struct vfio_dma, node);
> -
> + dma = rb_entry(node, struct vfio_dma, node);
> if (start + size <= dma->iova)
> node = node->rb_left;
> else if (start >= dma->iova + dma->size)
> node = node->rb_right;
> else
> - return dma;
> + break;
> }
> + if (!node)
> + return NULL;
> +
> + /* a dma slot intersects our window, check the type also matches */
> + if (type == VFIO_IOVA_ANY || dma->type == type)
> + return dma;
>
> return NULL;
> }
>
> +/**
> + * vfio_find_dma: find a dma slot intersecting a given window
> + * @iommu: vfio iommu handle
> + * @start: window base iova
> + * @size: window size
> + * @type: window type
> + */
> +static struct vfio_dma *vfio_find_dma(struct vfio_iommu *iommu,
> + dma_addr_t start, size_t size,
> + enum vfio_iova_type type)
> +{
> + struct rb_node *top_node = iommu->dma_list.rb_node;
> +
> + return vfio_find_dma_from_node(top_node, start, size, type);

nit, we could do without the top_node variable.

> +}
> +
> static void vfio_link_dma(struct vfio_iommu *iommu, struct vfio_dma *new)
> {
> struct rb_node **link = &iommu->dma_list.rb_node, *parent = NULL;
> @@ -484,19 +515,21 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
> * mappings within the range.
> */
> if (iommu->v2) {
> - dma = vfio_find_dma(iommu, unmap->iova, 0);
> + dma = vfio_find_dma(iommu, unmap->iova, 0, VFIO_IOVA_USER);
> if (dma && dma->iova != unmap->iova) {
> ret = -EINVAL;
> goto unlock;
> }
> - dma = vfio_find_dma(iommu, unmap->iova + unmap->size - 1, 0);
> + dma = vfio_find_dma(iommu, unmap->iova + unmap->size - 1, 0,
> + VFIO_IOVA_USER);
> if (dma && dma->iova + dma->size != unmap->iova + unmap->size) {
> ret = -EINVAL;
> goto unlock;
> }
> }
>
> - while ((dma = vfio_find_dma(iommu, unmap->iova, unmap->size))) {
> + while ((dma = vfio_find_dma(iommu, unmap->iova, unmap->size,
> + VFIO_IOVA_USER))) {
> if (!iommu->v2 && unmap->iova > dma->iova)
> break;
> unmapped += dma->size;
> @@ -600,7 +633,7 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
>
> mutex_lock(&iommu->lock);
>
> - if (vfio_find_dma(iommu, iova, size)) {
> + if (vfio_find_dma(iommu, iova, size, VFIO_IOVA_ANY)) {
> mutex_unlock(&iommu->lock);
> return -EEXIST;
> }