Re: [PATCH V3 5/9] vfio/type1: massage unmap iteration

[Alex Williamson <alex.williamson@redhat.com>]

On Fri, 29 Jan 2021 08:54:08 -0800
Steve Sistare <steven.sistare@oracle.com> wrote:

> Modify the iteration in vfio_dma_do_unmap so it does not depend on deletion
> of each dma entry.  Add a variant of vfio_find_dma that returns the entry
> with the lowest iova in the search range to initialize the iteration.  No
> externally visible change, but this behavior is needed in the subsequent
> update-vaddr patch.
> 
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 35 ++++++++++++++++++++++++++++++++++-
>  1 file changed, 34 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 407f0f7..5823607 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -173,6 +173,31 @@ static struct vfio_dma *vfio_find_dma(struct vfio_iommu *iommu,
>  	return NULL;
>  }
>  
> +static struct rb_node *vfio_find_dma_first(struct vfio_iommu *iommu,
> +					    dma_addr_t start, size_t size)

Nit, we return an rb_node rather than a vfio_dma now, but the naming is
still pretty similar to vfio_find_dma().  Can I change it to
vfio_find_dma_first_node() (yes, getting wordy)?  Thanks,

Alex

> +{
> +	struct rb_node *res = NULL;
> +	struct rb_node *node = iommu->dma_list.rb_node;
> +	struct vfio_dma *dma_res = NULL;
> +
> +	while (node) {
> +		struct vfio_dma *dma = rb_entry(node, struct vfio_dma, node);
> +
> +		if (start < dma->iova + dma->size) {
> +			res = node;
> +			dma_res = dma;
> +			if (start >= dma->iova)
> +				break;
> +			node = node->rb_left;
> +		} else {
> +			node = node->rb_right;
> +		}
> +	}
> +	if (res && size && dma_res->iova >= start + size)
> +		res = NULL;
> +	return res;
> +}
> +
>  static void vfio_link_dma(struct vfio_iommu *iommu, struct vfio_dma *new)
>  {
>  	struct rb_node **link = &iommu->dma_list.rb_node, *parent = NULL;
> @@ -1078,6 +1103,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
>  	dma_addr_t iova = unmap->iova;
>  	unsigned long size = unmap->size;
>  	bool unmap_all = !!(unmap->flags & VFIO_DMA_UNMAP_FLAG_ALL);
> +	struct rb_node *n;
>  
>  	mutex_lock(&iommu->lock);
>  
> @@ -1148,7 +1174,13 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
>  	}
>  
>  	ret = 0;
> -	while ((dma = vfio_find_dma(iommu, iova, size))) {
> +	n = vfio_find_dma_first(iommu, iova, size);
> +
> +	while (n) {
> +		dma = rb_entry(n, struct vfio_dma, node);
> +		if (dma->iova >= iova + size)
> +			break;
> +
>  		if (!iommu->v2 && iova > dma->iova)
>  			break;
>  		/*
> @@ -1193,6 +1225,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
>  		}
>  
>  		unmapped += dma->size;
> +		n = rb_next(n);
>  		vfio_remove_dma(iommu, dma);
>  	}
>