RE: [PATCH v5 2/7] vfio/type1: Check reserve region conflict and update iova list

[Tian, Kevin]

> From: Shameer Kolothum
> Sent: Friday, March 16, 2018 12:35 AM
> 
> This retrieves the reserved regions associated with dev group and
> checks for conflicts with any existing dma mappings. Also update
> the iova list excluding the reserved regions.
> 
> Signed-off-by: Shameer Kolothum
> <shameerali.kolothum.thodi@xxxxxxxxxx>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 90
> +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 90 insertions(+)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c
> b/drivers/vfio/vfio_iommu_type1.c
> index 1123c74..cfe2bb2 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -1313,6 +1313,82 @@ static int vfio_iommu_aper_resize(struct
> list_head *iova,
>  	return 0;
>  }
> 
> +/*
> + * Check reserved region conflicts with existing dma mappings
> + */
> +static bool vfio_iommu_resv_conflict(struct vfio_iommu *iommu,
> +				struct list_head *resv_regions)
> +{
> +	struct iommu_resv_region *region;
> +
> +	/* Check for conflict with existing dma mappings */
> +	list_for_each_entry(region, resv_regions, list) {
> +		if (vfio_find_dma(iommu, region->start, region->length))
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
> +/*
> + * Check iova region overlap with  reserved regions and
> + * exclude them from the iommu iova range
> + */
> +static int vfio_iommu_resv_exclude(struct list_head *iova,
> +					struct list_head *resv_regions)
> +{
> +	struct iommu_resv_region *resv;
> +	struct vfio_iova *n, *next;
> +
> +	list_for_each_entry(resv, resv_regions, list) {
> +		phys_addr_t start, end;
> +
> +		start = resv->start;
> +		end = resv->start + resv->length - 1;
> +
> +		list_for_each_entry_safe(n, next, iova, list) {
> +			int ret = 0;
> +
> +			/* No overlap */
> +			if ((start > n->end) || (end < n->start))
> +				continue;
> +			/*
> +			 * Insert a new node if current node overlaps with
> the
> +			 * reserve region to exlude that from valid iova
> range.
> +			 * Note that, new node is inserted before the
> current
> +			 * node and finally the current node is deleted
> keeping
> +			 * the list updated and sorted.
> +			 */
> +			if (start > n->start)
> +				ret = vfio_iommu_iova_insert(&n->list,
> +							n->start, start - 1);
> +			if (!ret && end < n->end)
> +				ret = vfio_iommu_iova_insert(&n->list,
> +							end + 1, n->end);
> +			if (ret)
> +				return ret;

Is it safer to delete the 1st node here in case of failure of the 2nd node?
There is no problem with current logic since upon error iova_copy will
be released anyway. However this function alone doesn't assume the
fact of a temporary list, thus it's better to keep the list clean w/o garbage
left from any error handling.

> +
> +			list_del(&n->list);
> +			kfree(n);
> +		}
> +	}
> +
> +	if (list_empty(iova))
> +		return -EINVAL;

if list_empty should BUG_ON here? or do we really need this check?

> +
> +	return 0;
> +}
> +
> +static void vfio_iommu_resv_free(struct list_head *resv_regions)
> +{
> +	struct iommu_resv_region *n, *next;
> +
> +	list_for_each_entry_safe(n, next, resv_regions, list) {
> +		list_del(&n->list);
> +		kfree(n);
> +	}
> +}
> +
>  static void vfio_iommu_iova_free(struct list_head *iova)
>  {
>  	struct vfio_iova *n, *next;
> @@ -1366,6 +1442,7 @@ static int vfio_iommu_type1_attach_group(void
> *iommu_data,
>  	phys_addr_t resv_msi_base;
>  	struct iommu_domain_geometry geo;
>  	LIST_HEAD(iova_copy);
> +	LIST_HEAD(group_resv_regions);
> 
>  	mutex_lock(&iommu->lock);
> 
> @@ -1444,6 +1521,13 @@ static int vfio_iommu_type1_attach_group(void
> *iommu_data,
>  		goto out_detach;
>  	}
> 
> +	iommu_get_group_resv_regions(iommu_group,
> &group_resv_regions);
> +
> +	if (vfio_iommu_resv_conflict(iommu, &group_resv_regions)) {
> +		ret = -EINVAL;
> +		goto out_detach;
> +	}
> +
>  	/* Get a copy of the current iova list and work on it */
>  	ret = vfio_iommu_iova_get_copy(iommu, &iova_copy);
>  	if (ret)
> @@ -1454,6 +1538,10 @@ static int vfio_iommu_type1_attach_group(void
> *iommu_data,
>  	if (ret)
>  		goto out_detach;
> 
> +	ret = vfio_iommu_resv_exclude(&iova_copy, &group_resv_regions);
> +	if (ret)
> +		goto out_detach;
> +
>  	resv_msi = vfio_iommu_has_sw_msi(iommu_group,
> &resv_msi_base);
> 
>  	INIT_LIST_HEAD(&domain->group_list);
> @@ -1514,6 +1602,7 @@ static int vfio_iommu_type1_attach_group(void
> *iommu_data,
>  	/* Delete the old one and insert new iova list */
>  	vfio_iommu_iova_insert_copy(iommu, &iova_copy);
>  	mutex_unlock(&iommu->lock);
> +	vfio_iommu_resv_free(&group_resv_regions);
> 
>  	return 0;
> 
> @@ -1522,6 +1611,7 @@ static int vfio_iommu_type1_attach_group(void
> *iommu_data,
>  out_domain:
>  	iommu_domain_free(domain->domain);
>  	vfio_iommu_iova_free(&iova_copy);
> +	vfio_iommu_resv_free(&group_resv_regions);
>  out_free:
>  	kfree(domain);
>  	kfree(group);
> --
> 2.7.4
> 
> 
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