[PATCH 2/2 v4] vfio-cdx: add ioctl support for bus master enable

[Nipun Gupta <nipun.gupta@amd.com>]

add VFIO_DEVICE_CDX_CTRL IOCTL to expose control operations for CDX
devices to VFIO users. Support Bus master enable and Bus master disable
on CDX bus control.

Signed-off-by: Shubham Rohila <shubham.rohila@amd.com>
Signed-off-by: Nipun Gupta <nipun.gupta@amd.com>
---

Changes in v4:
- This patch is newly added which uses cdx_set_master() and
  cdx_clear_master() APIs.

 drivers/vfio/cdx/main.c   | 26 ++++++++++++++++++++++++++
 include/uapi/linux/vfio.h | 14 ++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/drivers/vfio/cdx/main.c b/drivers/vfio/cdx/main.c
index c376a69d2db2..c39a965716f4 100644
--- a/drivers/vfio/cdx/main.c
+++ b/drivers/vfio/cdx/main.c
@@ -98,6 +98,30 @@ static int vfio_cdx_ioctl_get_region_info(struct vfio_cdx_device *vdev,
 	return copy_to_user(arg, &info, minsz) ? -EFAULT : 0;
 }
 
+static int vfio_cdx_ioctl_ctrl(struct vfio_cdx_device *vdev,
+			       struct vfio_device_cdx_ctrl __user *arg)
+{
+	unsigned long minsz = offsetofend(struct vfio_device_cdx_ctrl, op);
+	struct cdx_device *cdx_dev = to_cdx_device(vdev->vdev.dev);
+	struct vfio_device_cdx_ctrl ops;
+
+	if (copy_from_user(&ops, arg, minsz))
+		return -EFAULT;
+
+	if (ops.argsz < minsz)
+		return -EINVAL;
+
+	switch (ops.op) {
+	case VFIO_CDX_CTRL_CLEAR_MASTER:
+		cdx_clear_master(cdx_dev);
+		return 0;
+	case VFIO_CDX_CTRL_SET_MASTER:
+		return cdx_set_master(cdx_dev);
+	default:
+		return -EINVAL;
+	}
+}
+
 static long vfio_cdx_ioctl(struct vfio_device *core_vdev,
 			   unsigned int cmd, unsigned long arg)
 {
@@ -112,6 +136,8 @@ static long vfio_cdx_ioctl(struct vfio_device *core_vdev,
 		return vfio_cdx_ioctl_get_region_info(vdev, uarg);
 	case VFIO_DEVICE_RESET:
 		return cdx_dev_reset(core_vdev->dev);
+	case VFIO_DEVICE_CDX_CTRL:
+		return vfio_cdx_ioctl_ctrl(vdev, uarg);
 	default:
 		return -ENOTTY;
 	}
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 20c804bdc09c..5f6a58f9f8e2 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -1649,6 +1649,20 @@ struct vfio_iommu_spapr_tce_remove {
 };
 #define VFIO_IOMMU_SPAPR_TCE_REMOVE	_IO(VFIO_TYPE, VFIO_BASE + 20)
 
+/**
+ * VFIO_DEVICE_CDX_CTRL - _IO(VFIO_TYPE, VFIO_BASE + 21)
+ *
+ * Control CDX device.
+ * Variable op is set as per the operation required
+ */
+struct vfio_device_cdx_ctrl {
+	__u32 argsz;
+	__u32 op;
+#define	VFIO_CDX_CTRL_SET_MASTER	0	/* Set Bus Master */
+#define	VFIO_CDX_CTRL_CLEAR_MASTER	1	/* Clear Bus Master */
+};
+#define VFIO_DEVICE_CDX_CTRL		_IO(VFIO_TYPE, VFIO_BASE + 21)
+
 /* ***************************************************************** */
 
 #endif /* _UAPIVFIO_H */
-- 
2.17.1