This op does the copy to/from user for the info and can return back
a cap chain through a vfio_info_cap * result.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/vfio/vfio_main.c | 54 +++++++++++++++++++++++++++++++++++++---
 include/linux/vfio.h     |  4 +++
 2 files changed, 54 insertions(+), 4 deletions(-)

diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
index f056e82ba35075..82e7d79b1f9fe2 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -1259,6 +1259,55 @@ static int vfio_ioctl_device_feature(struct vfio_device *device,
 	}
 }
 
+static long vfio_get_region_info(struct vfio_device *device,
+				 struct vfio_region_info __user *arg)
+{
+	unsigned long minsz = offsetofend(struct vfio_region_info, offset);
+	struct vfio_region_info info = {};
+	int ret;
+
+	if (copy_from_user(&info, arg, minsz))
+		return -EFAULT;
+	if (info.argsz < minsz)
+		return -EINVAL;
+
+	if (device->ops->get_region_info_caps) {
+		struct vfio_info_cap caps = { .buf = NULL, .size = 0 };
+
+		ret = device->ops->get_region_info_caps(device, &info, &caps);
+		if (ret)
+			return ret;
+
+		if (caps.size) {
+			info.flags |= VFIO_REGION_INFO_FLAG_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(arg + 1, caps.buf,
+						 caps.size)) {
+					kfree(caps.buf);
+					return -EFAULT;
+				}
+				info.cap_offset = sizeof(info);
+			}
+			kfree(caps.buf);
+		}
+
+		if (copy_to_user(arg, &info, minsz))
+			return -EFAULT;
+	} else if (device->ops->get_region_info) {
+		ret = device->ops->get_region_info(device, arg);
+		if (ret)
+			return ret;
+	} else {
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static long vfio_device_fops_unl_ioctl(struct file *filep,
 				       unsigned int cmd, unsigned long arg)
 {
@@ -1297,10 +1346,7 @@ static long vfio_device_fops_unl_ioctl(struct file *filep,
 		break;
 
 	case VFIO_DEVICE_GET_REGION_INFO:
-		if (unlikely(!device->ops->get_region_info))
-			ret = -EINVAL;
-		else
-			ret = device->ops->get_region_info(device, uptr);
+		ret = vfio_get_region_info(device, uptr);
 		break;
 
 	default:
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index be5fcf8432e8d5..6311ddc837701d 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -21,6 +21,7 @@ struct kvm;
 struct iommufd_ctx;
 struct iommufd_device;
 struct iommufd_access;
+struct vfio_info_cap;
 
 /*
  * VFIO devices can be placed in a set, this allows all devices to share this
@@ -134,6 +135,9 @@ struct vfio_device_ops {
 			 unsigned long arg);
 	int	(*get_region_info)(struct vfio_device *vdev,
 				   struct vfio_region_info __user *arg);
+	int	(*get_region_info_caps)(struct vfio_device *vdev,
+					struct vfio_region_info *info,
+					struct vfio_info_cap *caps);
 	int	(*mmap)(struct vfio_device *vdev, struct vm_area_struct *vma);
 	void	(*request)(struct vfio_device *vdev, unsigned int count);
 	int	(*match)(struct vfio_device *vdev, char *buf);
-- 
2.43.0