[RFC] vfio/type1: Add IOVA_RANGE capability support

[Shameer Kolothum]

This patch allows the user-space to retrieve the supported
IOVA range(s), excluding any reserved regions. The implementation
is based on capability chains, added to the VFIO_IOMMU_GET_INFO ioctl.

This is following the discussions here[1] and is based on the RFC patch[2].

ToDo:
 - This currently derives the default supported iova range from the first
   iommu domain. This needs to be changed to go through the domain_list
   instead.
 - Sync with Pierre's patch[3].

1.https://lists.gnu.org/archive/html/qemu-devel/2017-11/msg03651.html
2.https://lists.linuxfoundation.org/pipermail/iommu/2016-November/019002.html
3.https://patchwork.kernel.org/patch/10084655/

Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx>
---
 drivers/vfio/vfio_iommu_type1.c | 172 +++++++++++++++++++++++++++++++++++++++-
 include/uapi/linux/vfio.h       |  13 +++
 2 files changed, 184 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index e30e29a..72ca78a 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -28,6 +28,7 @@
 #include <linux/device.h>
 #include <linux/fs.h>
 #include <linux/iommu.h>
+#include <linux/list_sort.h>
 #include <linux/module.h>
 #include <linux/mm.h>
 #include <linux/rbtree.h>
@@ -92,6 +93,12 @@ struct vfio_group {
 	struct list_head	next;
 };
 
+struct vfio_iommu_iova {
+	struct list_head	list;
+	phys_addr_t		start;
+	phys_addr_t		end;
+};
+
 /*
  * Guest RAM pinning working set or DMA target
  */
@@ -1537,6 +1544,144 @@ static int vfio_domains_have_iommu_cache(struct vfio_iommu *iommu)
 	return ret;
 }
 
+static int vfio_add_iova_cap(struct vfio_info_cap *caps, u64 start, u64 end)
+{
+	struct vfio_iommu_type1_info_cap_iova_range *cap;
+	struct vfio_info_cap_header *header;
+
+	header = vfio_info_cap_add(caps, sizeof(*cap),
+			VFIO_IOMMU_TYPE1_INFO_CAP_IOVA_RANGE, 1);
+	if (IS_ERR(header))
+		return PTR_ERR(header);
+
+	cap = container_of(header,
+			   struct vfio_iommu_type1_info_cap_iova_range,
+			   header);
+
+	cap->start = start;
+	cap->end = end;
+
+	return 0;
+}
+
+static int vfio_insert_iova(phys_addr_t start, phys_addr_t end,
+				struct list_head *head)
+{
+	struct vfio_iommu_iova *region;
+
+	region = kzalloc(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 and update iova region list in case a reserved region
+ * overlaps the iommu iova range.
+ */
+static int vfio_update_iommu_iova_range(phys_addr_t start, phys_addr_t end,
+					struct list_head *iova)
+{
+	struct vfio_iommu_iova *node;
+	phys_addr_t a, b;
+	int ret = 0;
+
+	if (list_empty(iova))
+		return -ENODEV;
+
+	node = list_last_entry(iova, struct vfio_iommu_iova, list);
+	a = node->start;
+	b = node->end;
+
+	/* No overlap */
+	if ((start > b) || (end < a))
+		return 0;
+
+	if (start > a)
+		ret = vfio_insert_iova(a, start - 1, &node->list);
+	if (ret)
+		goto done;
+	if (end < b)
+		ret = vfio_insert_iova(end + 1, b, &node->list);
+
+done:
+	list_del(&node->list);
+	kfree(node);
+
+	return ret;
+}
+
+static int vfio_resv_cmp(void *priv, struct list_head *a, struct list_head *b)
+{
+	struct iommu_resv_region *ra, *rb;
+
+	ra = container_of(a, struct iommu_resv_region, list);
+	rb = container_of(b, struct iommu_resv_region, list);
+
+	if (ra->start < rb->start)
+		return -1;
+	if (ra->start > rb->start)
+		return 1;
+	return 0;
+}
+
+static int vfio_build_iommu_iova_caps(struct vfio_iommu *iommu,
+				struct vfio_info_cap *caps)
+{
+	struct iommu_resv_region *resv, *resv_next;
+	struct vfio_iommu_iova *iova, *iova_next;
+	struct list_head group_resv_regions, vfio_iova_regions;
+	struct vfio_domain *domain;
+	struct vfio_group *g;
+	phys_addr_t start, end;
+	int ret = 0;
+
+	domain = list_first_entry(&iommu->domain_list,
+				  struct vfio_domain, next);
+	/* Get the default iova range supported */
+	start = domain->domain->geometry.aperture_start;
+	end = domain->domain->geometry.aperture_end;
+	INIT_LIST_HEAD(&vfio_iova_regions);
+	vfio_insert_iova(start, end, &vfio_iova_regions);
+
+	/* Get reserved regions if any */
+	INIT_LIST_HEAD(&group_resv_regions);
+	list_for_each_entry(g, &domain->group_list, next)
+		iommu_get_group_resv_regions(g->iommu_group,
+						&group_resv_regions);
+	list_sort(NULL, &group_resv_regions, vfio_resv_cmp);
+
+	/* Update iova range excluding reserved regions */
+	list_for_each_entry(resv, &group_resv_regions, list) {
+		ret = vfio_update_iommu_iova_range(resv->start,
+				resv->start + resv->length - 1,
+				&vfio_iova_regions);
+		if (ret)
+			goto done;
+	}
+
+	list_for_each_entry(iova, &vfio_iova_regions, list) {
+		ret = vfio_add_iova_cap(caps, iova->start, iova->end);
+		if (ret)
+			goto done;
+	}
+
+done:
+	list_for_each_entry_safe(resv, resv_next, &group_resv_regions, list)
+		kfree(resv);
+
+	list_for_each_entry_safe(iova, iova_next, &vfio_iova_regions, list)
+		kfree(iova);
+
+	return ret;
+}
+
 static long vfio_iommu_type1_ioctl(void *iommu_data,
 				   unsigned int cmd, unsigned long arg)
 {
@@ -1558,8 +1703,10 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 		}
 	} else if (cmd == VFIO_IOMMU_GET_INFO) {
 		struct vfio_iommu_type1_info info;
+		struct vfio_info_cap caps = { .buf = NULL, .size = 0 };
+		int ret;
 
-		minsz = offsetofend(struct vfio_iommu_type1_info, iova_pgsizes);
+		minsz = offsetofend(struct vfio_iommu_type1_info, cap_offset);
 
 		if (copy_from_user(&info, (void __user *)arg, minsz))
 			return -EFAULT;
@@ -1571,6 +1718,29 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 
 		info.iova_pgsizes = vfio_pgsize_bitmap(iommu);
 
+		ret = vfio_build_iommu_iova_caps(iommu, &caps);
+		if (ret)
+			return ret;
+
+		if (caps.size) {
+			info.flags |= VFIO_IOMMU_INFO_CAPS;
+			if (info.argsz < sizeof(info) + caps.size) {
+				info.argsz = sizeof(info) + caps.size;
+				info.cap_offset = 0;
+			} else {
+				vfio_info_cap_shift(&caps, sizeof(info));
+				if (copy_to_user((void __user *)arg +
+						sizeof(info), caps.buf,
+						caps.size)) {
+					kfree(caps.buf);
+					return -EFAULT;
+				}
+				info.cap_offset = sizeof(info);
+			}
+
+			kfree(caps.buf);
+		}
+
 		return copy_to_user((void __user *)arg, &info, minsz) ?
 			-EFAULT : 0;
 
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index e3301db..c4e338b 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -517,7 +517,20 @@ struct vfio_iommu_type1_info {
 	__u32	argsz;
 	__u32	flags;
 #define VFIO_IOMMU_INFO_PGSIZES (1 << 0)	/* supported page sizes info */
+#define VFIO_IOMMU_INFO_CAPS	(1 << 1)	/* Info supports caps */
 	__u64	iova_pgsizes;		/* Bitmap of supported page sizes */
+	__u32   cap_offset;	/* Offset within info struct of first cap */
+	__u32	__resv;
+};
+
+/*
+ * The IOVA_RANGE capability allows to report the IOVA range(s),
+ */
+#define VFIO_IOMMU_TYPE1_INFO_CAP_IOVA_RANGE  1
+struct vfio_iommu_type1_info_cap_iova_range {
+	struct vfio_info_cap_header header;
+	__u64 start;
+	__u64 end;
 };
 
 #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12)
-- 
1.9.1