[RFC v2 4/5] vfio/type1: Add IOVA range capability support

[Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx>]

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

Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx>
---
 drivers/vfio/vfio_iommu_type1.c | 91 +++++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/vfio.h       | 23 +++++++++++
 2 files changed, 114 insertions(+)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 47ea490..dc6ed85 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -1893,6 +1893,67 @@ static int vfio_domains_have_iommu_cache(struct vfio_iommu *iommu)
 	return ret;
 }
 
+static int vfio_add_iova_cap(struct vfio_info_cap *caps, void *cap_type,
+			     size_t size)
+{
+	struct vfio_info_cap_header *header;
+	struct vfio_iommu_type1_info_cap_iova *iova_cap, *iova = cap_type;
+
+	header = vfio_info_cap_add(caps, size,
+				VFIO_IOMMU_TYPE1_INFO_CAP_IOVA, 1);
+	if (IS_ERR(header))
+		return PTR_ERR(header);
+
+	iova_cap = container_of(header,
+			struct vfio_iommu_type1_info_cap_iova, header);
+	iova_cap->nr_iovas = iova->nr_iovas;
+	memcpy(iova_cap->iova_ranges, iova->iova_ranges,
+			iova->nr_iovas * sizeof(*iova->iova_ranges));
+	return 0;
+}
+
+static int vfio_build_iommu_iova_caps(struct vfio_iommu *iommu,
+				struct vfio_info_cap *caps)
+{
+	struct vfio_iommu_type1_info_cap_iova *iova_cap;
+	struct vfio_iova *iova;
+	size_t size;
+	int iovas = 0, i = 0, ret;
+
+	mutex_lock(&iommu->lock);
+
+	list_for_each_entry(iova, &iommu->iova_list, list)
+		iovas++;
+
+	if (!iovas) {
+		ret = EINVAL;
+		goto out_unlock;
+	}
+
+	size = sizeof(*iova_cap) + (iovas * sizeof(*iova_cap->iova_ranges));
+
+	iova_cap = kzalloc(size, GFP_KERNEL);
+	if (!iova_cap) {
+		ret = -ENOMEM;
+		goto out_unlock;
+	}
+
+	iova_cap->nr_iovas = iovas;
+
+	list_for_each_entry(iova, &iommu->iova_list, list) {
+		iova_cap->iova_ranges[i].start = iova->start;
+		iova_cap->iova_ranges[i].end = iova->end;
+		i++;
+	}
+
+	ret = vfio_add_iova_cap(caps, iova_cap, size);
+
+	kfree(iova_cap);
+out_unlock:
+	mutex_unlock(&iommu->lock);
+	return ret;
+}
+
 static long vfio_iommu_type1_ioctl(void *iommu_data,
 				   unsigned int cmd, unsigned long arg)
 {
@@ -1914,6 +1975,8 @@ 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);
 
@@ -1927,6 +1990,34 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 
 		info.iova_pgsizes = vfio_pgsize_bitmap(iommu);
 
+		if (info.argsz == minsz)
+			goto done;
+
+		ret = vfio_build_iommu_iova_caps(iommu, &caps);
+		if (ret)
+			return ret;
+
+		if (caps.size) {
+			info.flags |= VFIO_IOMMU_INFO_CAPS;
+			minsz = offsetofend(struct vfio_iommu_type1_info,
+							 cap_offset);
+			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);
+		}
+done:
 		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..8671448 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -517,7 +517,30 @@ 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 */
+};
+
+/*
+ * The IOVA capability allows to report the valid IOVA range(s)
+ * excluding any reserved regions associated with dev group. Any dma
+ * map attempt outside the valid iova range will return error.
+ *
+ * The structures below define version 1 of this capability.
+ */
+#define VFIO_IOMMU_TYPE1_INFO_CAP_IOVA  1
+
+struct vfio_iova_range {
+	__u64	start;
+	__u64	end;
+};
+
+struct vfio_iommu_type1_info_cap_iova {
+	struct vfio_info_cap_header header;
+	__u32	nr_iovas;
+	__u32	reserved;
+	struct vfio_iova_range iova_ranges[];
 };
 
 #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12)
-- 
1.9.1