[PATCH 4/6] vduse: Support querying IOLTB information

[Xie Yongji <xieyongji@bytedance.com>]

This introduces a new ioctl: VDUSE_IOTLB_GET_INFO to
support querying IOLTB information such as bounce
buffer size.

Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
---
 drivers/vdpa/vdpa_user/vduse_dev.c | 13 +++++++++++++
 include/uapi/linux/vduse.h         | 17 +++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
index 3bc27de58f46..c47a5d9765cf 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -1089,6 +1089,19 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
 		ret = vduse_dev_queue_irq_work(dev, &dev->vqs[index].inject);
 		break;
 	}
+	case VDUSE_IOTLB_GET_INFO: {
+		struct vduse_iotlb_info iotlb;
+
+		iotlb.bounce_iova = 0;
+		iotlb.bounce_size = dev->domain->bounce_size;
+
+		ret = -EFAULT;
+		if (copy_to_user(argp, &iotlb, sizeof(iotlb)))
+			break;
+
+		ret = 0;
+		break;
+	}
 	default:
 		ret = -ENOIOCTLCMD;
 		break;
diff --git a/include/uapi/linux/vduse.h b/include/uapi/linux/vduse.h
index 7cfe1c1280c0..c201b7a77c2c 100644
--- a/include/uapi/linux/vduse.h
+++ b/include/uapi/linux/vduse.h
@@ -210,6 +210,23 @@ struct vduse_vq_eventfd {
  */
 #define VDUSE_VQ_INJECT_IRQ	_IOW(VDUSE_BASE, 0x17, __u32)
 
+/**
+ * struct vduse_iotlb_info - IOTLB information
+ * @bounce_iova: start IOVA of bounce buffer
+ * @bounce_size: bounce buffer size
+ * @reserved: for future use, needs to be initialized to zero
+ *
+ * Structure used by VDUSE_IOTLB_GET_INFO ioctl to get IOTLB information.
+ */
+struct vduse_iotlb_info {
+	__u64 bounce_iova;
+	__u64 bounce_size;
+	__u64 reserved[2];
+};
+
+/* Get IOTLB information, e.g. bounce buffer size */
+#define VDUSE_IOTLB_GET_INFO    _IOR(VDUSE_BASE, 0x18, struct vduse_iotlb_info)
+
 /* The control messages definition for read(2)/write(2) on /dev/vduse/$NAME */
 
 /**
-- 
2.20.1