linux-kernel - Re: [PATCH v13 10/15] vfio/type1: Implement recursive vfio_find_dma_from

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Date:   Thu, 6 Oct 2016 14:19:00 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Eric Auger <eric.auger@...hat.com>
Cc:     eric.auger.pro@...il.com, christoffer.dall@...aro.org,
        marc.zyngier@....com, robin.murphy@....com, will.deacon@....com,
        joro@...tes.org, tglx@...utronix.de, jason@...edaemon.net,
        linux-arm-kernel@...ts.infradead.org, kvm@...r.kernel.org,
        drjones@...hat.com, linux-kernel@...r.kernel.org,
        Bharat.Bhushan@...escale.com, pranav.sawargaonkar@...il.com,
        p.fedin@...sung.com, iommu@...ts.linux-foundation.org,
        Jean-Philippe.Brucker@....com, yehuday@...vell.com,
        Manish.Jaggi@...iumnetworks.com
Subject: Re: [PATCH v13 10/15] vfio/type1: Implement recursive
 vfio_find_dma_from_node

On Thu,  6 Oct 2016 08:45:26 +0000
Eric Auger <eric.auger@...hat.com> wrote:

> This patch handles the case where a node is encountered, matching
> @start and @size arguments but not matching the @type argument.
> In that case, we need to skip that node and pursue the search in the
> node's leaves. In case @start is inferior to the node's base, we
> resume the search on the left leaf. If the recursive search on the left
> leaves did not produce any match, we search the right leaves recursively.
> 
> Signed-off-by: Eric Auger <eric.auger@...hat.com>

Acked-by: Alex Williamson <alex.williamson@...hat.com>
 
> ---
> 
> v10: creation
> ---
>  drivers/vfio/vfio_iommu_type1.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index cb7267a..65a4038 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -125,7 +125,17 @@ static struct vfio_dma *vfio_find_dma_from_node(struct rb_node *top,
>  	if (type == VFIO_IOVA_ANY || dma->type == type)
>  		return dma;
>  
> -	return NULL;
> +	/* restart 2 searches skipping the current node */
> +	if (start < dma->iova) {
> +		dma = vfio_find_dma_from_node(node->rb_left, start,
> +					      size, type);
> +		if (dma)
> +			return dma;
> +	}
> +	if (start + size > dma->iova + dma->size)
> +		dma = vfio_find_dma_from_node(node->rb_right, start,
> +					      size, type);
> +	return dma;
>  }
>  
>  /**