Re: [PATCH v3 1/6] vfio/type1: Introduce iova list and add iommu aperture validity check

[Alex Williamson]

On Thu, 15 Feb 2018 09:44:59 +0000
Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx> wrote:

> This introduces an iova list that is valid for dma mappings. Make
> sure the new iommu aperture window doesn't conflict with the current
> one or with any existing dma mappings during attach.
> 
> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 183 +++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 181 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index e30e29a..4726f55 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -60,6 +60,7 @@ MODULE_PARM_DESC(disable_hugepages,
>  
>  struct vfio_iommu {
>  	struct list_head	domain_list;
> +	struct list_head	iova_list;
>  	struct vfio_domain	*external_domain; /* domain for external user */
>  	struct mutex		lock;
>  	struct rb_root		dma_list;
> @@ -92,6 +93,12 @@ struct vfio_group {
>  	struct list_head	next;
>  };
>  
> +struct vfio_iova {
> +	struct list_head	list;
> +	dma_addr_t		start;
> +	dma_addr_t		end;
> +};
> +
>  /*
>   * Guest RAM pinning working set or DMA target
>   */
> @@ -1192,6 +1199,142 @@ static bool vfio_iommu_has_sw_msi(struct iommu_group *group, phys_addr_t *base)
>  	return ret;
>  }
>  
> +/*
> + * This is a helper function to insert an address range to iova list.
> + * The list starts with a single entry corresponding to the IOMMU
> + * domain geometry to which the device group is attached. The list
> + * aperture gets modified when a new domain is added to the container
> + * if the new aperture doesn't conflict with the current one or with
> + * any existing dma mappings. The list is also modified to exclude
> + * any reserved regions associated with the device group.
> + */
> +static int vfio_insert_iova(phys_addr_t start, phys_addr_t end,
> +				struct list_head *head)

The args seem more natural to me and have better consistency with the
other functions re-ordered as (head, start, end).

Also, if the iova list is dma_addr_t, why are we using phys_addr_t for
args?

> +{
> +	struct vfio_iova *region;
> +
> +	region = kmalloc(sizeof(*region), GFP_KERNEL);
> +	if (!region)
> +		return -ENOMEM;
> +
> +	INIT_LIST_HEAD(&region->list);
> +	region->start = start;
> +	region->end = end;
> +
> +	list_add_tail(&region->list, head);
> +	return 0;
> +}
> +
> +/*
> + * Check the new iommu aperture conflicts with existing aper or
> + * with any existing dma mappings.
> + */
> +static bool vfio_iommu_aper_conflict(struct vfio_iommu *iommu,
> +				     phys_addr_t start,
> +				     phys_addr_t end)

Same here, why phys_addr_t when comparing to dma_addr_t?

> +{
> +	struct vfio_iova *first, *last;
> +	struct list_head *iova = &iommu->iova_list;
> +
> +	if (list_empty(iova))
> +		return false;
> +
> +	/* Disjoint sets, return conflict */
> +	first = list_first_entry(iova, struct vfio_iova, list);
> +	last = list_last_entry(iova, struct vfio_iova, list);
> +	if ((start > last->end) || (end < first->start))
> +		return true;
> +
> +	/* Check for any existing dma mappings outside the new start */
> +	if (start > first->start) {
> +		if (vfio_find_dma(iommu, first->start, start - first->start))
> +			return true;
> +	}
> +
> +	/* Check for any existing dma mappings outside the new end */
> +	if (end < last->end) {
> +		if (vfio_find_dma(iommu, end + 1, last->end - end))
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
> +/*
> + * Resize iommu iova aperture window. This is called only if the new
> + * aperture has no conflict with existing aperture and dma mappings.
> + */
> +static int vfio_iommu_aper_resize(struct list_head *iova,
> +				      dma_addr_t start,
> +				      dma_addr_t end)

And here we're back to dma_addr_t, let's be consistent.

> +{
> +	struct vfio_iova *node, *next;
> +
> +	if (list_empty(iova))
> +		return vfio_insert_iova(start, end, iova);
> +
> +	/* Adjust iova list start */
> +	list_for_each_entry_safe(node, next, iova, list) {
> +		if (start < node->start)
> +			break;
> +		if ((start >= node->start) && (start < node->end)) {
> +			node->start = start;
> +			break;
> +		}
> +		/* Delete nodes before new start */
> +		list_del(&node->list);
> +		kfree(node);
> +	}
> +
> +	/* Adjust iova list end */
> +	list_for_each_entry_safe(node, next, iova, list) {
> +		if (end > node->end)
> +			continue;
> +

nit, extra blank line vs block above.

> +		if ((end >= node->start) && (end < node->end)) {

This test is still incorrect, if end == node->start, we get a zero
sized range, we should have let it pass over to get deleted.  Therefore
the first test should be (end > node->start).  The second test was
changed and is now incorrect, if end == node->end, then we want to keep
this range, not delete it.  This test should have remained (end <=
node->end) as it was in the previous version.  IOW, my previous comment
was applied to the wrong test.

> +			node->end = end;
> +			continue;
> +		}
> +		/* Delete nodes after new end */
> +		list_del(&node->list);
> +		kfree(node);
> +	}
> +
> +	return 0;
> +}
> +
> +static int vfio_iommu_get_iova_copy(struct vfio_iommu *iommu,
> +				struct list_head *iova_copy)
> +{
> +
> +	struct list_head *iova = &iommu->iova_list;
> +	struct vfio_iova *n;
> +
> +	list_for_each_entry(n, iova, list) {
> +		int ret;
> +
> +		ret = vfio_insert_iova(n->start, n->end, iova_copy);
> +		if (ret)
> +			return ret;

Let's delete and free any entries added to the copy here too.

> +	}
> +
> +	return 0;
> +}
> +
> +static void vfio_iommu_insert_iova_copy(struct vfio_iommu *iommu,
> +					struct list_head *iova_copy)
> +{
> +	struct list_head *iova = &iommu->iova_list;
> +	struct vfio_iova *n, *next;
> +
> +	list_for_each_entry_safe(n, next, iova, list) {
> +		list_del(&n->list);
> +		kfree(n);
> +	}
> +
> +	list_splice_tail(iova_copy, iova);
> +}
> +
>  static int vfio_iommu_type1_attach_group(void *iommu_data,
>  					 struct iommu_group *iommu_group)
>  {
> @@ -1202,6 +1345,9 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
>  	int ret;
>  	bool resv_msi, msi_remap;
>  	phys_addr_t resv_msi_base;
> +	struct iommu_domain_geometry geo;
> +	struct list_head iova_copy;
> +	struct vfio_iova *iova, *iova_next;
>  
>  	mutex_lock(&iommu->lock);
>  
> @@ -1271,6 +1417,26 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
>  	if (ret)
>  		goto out_domain;
>  
> +	/* Get aperture info */
> +	iommu_domain_get_attr(domain->domain, DOMAIN_ATTR_GEOMETRY, &geo);
> +
> +	if (vfio_iommu_aper_conflict(iommu, geo.aperture_start,
> +					    geo.aperture_end)) {
> +		ret = -EINVAL;
> +		goto out_detach;
> +	}
> +
> +	/* Get a copy of the current iova list and work on it */
> +	INIT_LIST_HEAD(&iova_copy);

We could have just declared this as:

LIST_HEAD(iova_copy);

to avoid needing to init it separately.

> +	ret = vfio_iommu_get_iova_copy(iommu, &iova_copy);
> +	if (ret)
> +		goto out_detach;
> +
> +	ret = vfio_iommu_aper_resize(&iova_copy, geo.aperture_start,
> +							geo.aperture_end);
> +	if (ret)
> +		goto out_detach;
> +
>  	resv_msi = vfio_iommu_has_sw_msi(iommu_group, &resv_msi_base);
>  
>  	INIT_LIST_HEAD(&domain->group_list);
> @@ -1304,8 +1470,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
>  				list_add(&group->next, &d->group_list);
>  				iommu_domain_free(domain->domain);
>  				kfree(domain);
> -				mutex_unlock(&iommu->lock);
> -				return 0;
> +				goto done;
>  			}
>  
>  			ret = iommu_attach_group(domain->domain, iommu_group);
> @@ -1328,6 +1493,9 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
>  	}
>  
>  	list_add(&domain->next, &iommu->domain_list);
> +done:
> +	/* Delete the old one and insert new iova list */
> +	vfio_iommu_insert_iova_copy(iommu, &iova_copy);
>  
>  	mutex_unlock(&iommu->lock);
>  
> @@ -1337,6 +1505,8 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
>  	iommu_detach_group(domain->domain, iommu_group);
>  out_domain:
>  	iommu_domain_free(domain->domain);
> +	list_for_each_entry_safe(iova, iova_next, &iova_copy, list)
> +		kfree(iova);

Let's do the list_del() too, it's making me squirm that it's not here
and this is not a performance path.

>  out_free:
>  	kfree(domain);
>  	kfree(group);
> @@ -1475,6 +1645,7 @@ static void *vfio_iommu_type1_open(unsigned long arg)
>  	}
>  
>  	INIT_LIST_HEAD(&iommu->domain_list);
> +	INIT_LIST_HEAD(&iommu->iova_list);
>  	iommu->dma_list = RB_ROOT;
>  	mutex_init(&iommu->lock);
>  	BLOCKING_INIT_NOTIFIER_HEAD(&iommu->notifier);
> @@ -1502,6 +1673,7 @@ static void vfio_iommu_type1_release(void *iommu_data)
>  {
>  	struct vfio_iommu *iommu = iommu_data;
>  	struct vfio_domain *domain, *domain_tmp;
> +	struct vfio_iova *iova, *iova_next;
>  
>  	if (iommu->external_domain) {
>  		vfio_release_domain(iommu->external_domain, true);
> @@ -1517,6 +1689,13 @@ static void vfio_iommu_type1_release(void *iommu_data)
>  		list_del(&domain->next);
>  		kfree(domain);
>  	}
> +
> +	list_for_each_entry_safe(iova, iova_next,
> +				 &iommu->iova_list, list) {
> +		list_del(&iova->list);
> +		kfree(iova);
> +	}
> +
>  	kfree(iommu);
>  }
>