linux-kernel - Re: [PATCH v9 2/7] vfio/type1: vfio_find

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Message-ID: <20160509164928.518a05a8@t450s.home>
Date:	Mon, 9 May 2016 16:49:28 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	Eric Auger <eric.auger@...aro.org>
Cc:	eric.auger@...com, robin.murphy@....com, will.deacon@....com,
	joro@...tes.org, tglx@...utronix.de, jason@...edaemon.net,
	marc.zyngier@....com, christoffer.dall@...aro.org,
	linux-arm-kernel@...ts.infradead.org, patches@...aro.org,
	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,
	julien.grall@....com, yehuday@...vell.com
Subject: Re: [PATCH v9 2/7] vfio/type1: vfio_find_dma accepting a type
 argument

On Wed,  4 May 2016 11:54:13 +0000
Eric Auger <eric.auger@...aro.org> wrote:

> In our RB-tree we now have 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 proposes an implementation for that modality and also
> changes the existing callers using the USER type.
> 
> Signed-off-by: Eric Auger <eric.auger@...aro.org>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 63 ++++++++++++++++++++++++++++++++++-------
>  1 file changed, 53 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index aaf5a6c..2d769d4 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -98,23 +98,64 @@ 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
> +			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;
> +
> +	/* 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);

It might be nice to split this little bit of trickery out to a separate
patch so that you can better explain what it does.  It's really not
needed until we start creating user-type entries, so it shouldn't hurt
bisection.

> +	return dma;
> +}
> +
> +/**
> + * 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 NULL;
> +	return vfio_find_dma_from_node(top_node, start, size, type);
>  }
>  
>  static void vfio_link_dma(struct vfio_iommu *iommu, struct vfio_dma *new)
> @@ -488,19 +529,21 @@ 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;
> @@ -604,7 +647,7 @@ 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;
>  	}