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

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Message-ID: <5731F60B.6040105@linaro.org>
Date:	Tue, 10 May 2016 16:54:03 +0200
From:	Eric Auger <eric.auger@...aro.org>
To:	Alex Williamson <alex.williamson@...hat.com>
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

Hi Alex,
On 05/10/2016 12:49 AM, Alex Williamson wrote:
> 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.
OK I will

Regards

Eric
> 
>> +	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;
>>  	}
>