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

Shameerali Kolothum Thodi
2018-03-19T10:55:41Z

> -----Original Message-----
> From: Tian, Kevin [mailto:kevin.tian-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org]
> Sent: Monday, March 19, 2018 7:52 AM
> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>;
> alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org; eric.auger-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org;
> pmorel-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org
> Cc: kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; xuwei (O)
> <xuwei5-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>; Linuxarm <linuxarm-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>;
> iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
> 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-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
> > ---
> > 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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