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

[Shameerali Kolothum Thodi]

> -----Original Message-----
> From: Tian, Kevin [mailto:kevin.tian@xxxxxxxxx]
> Sent: Monday, March 19, 2018 7:52 AM
> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx>;
> alex.williamson@xxxxxxxxxx; eric.auger@xxxxxxxxxx;
> pmorel@xxxxxxxxxxxxxxxxxx
> Cc: kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; xuwei (O)
> <xuwei5@xxxxxxxxxx>; Linuxarm <linuxarm@xxxxxxxxxx>;
> iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx
> Subject: RE: [PATCH v5 2/7] vfio/type1: Check reserve region conflict and
> update iova list
> 
> > 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.

Agree. I will consider this.

> > +
> > +			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?

I think we need the check here. This basically means there is no valid iova
region as the reserved regions overlaps it completely(very unlikely, a bad
configuration maybe). The __attach will fail if that happens and may be 
WARN_ON is a good idea to notify the user.

Thanks,
Shameer

> > +
> > +	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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> > iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx
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