[PATCH v7 3/3] vfio-cdx: add bus mastering device feature support

[Nipun Gupta]

Support Bus master enable and disable on VFIO-CDX devices using
VFIO_DEVICE_FEATURE_BUS_MASTER flag over VFIO_DEVICE_FEATURE IOCTL.

Co-developed-by: Shubham Rohila <shubham.rohila@xxxxxxx>
Signed-off-by: Shubham Rohila <shubham.rohila@xxxxxxx>
Signed-off-by: Nipun Gupta <nipun.gupta@xxxxxxx>
---

Changes v6->v7:
- Add check for BME in open, thus resulting in correct response
  in feature probe.
- Set vdev_regions to NULL in case of error in vfio device open.

Changes v5->v6:
- Called CDX device reset at cdx_open_device()

Changes v4->v5:
- Use device feature IOCTL instead of adding a new VFIO IOCTL
  for bus master feature.

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

 drivers/vfio/cdx/main.c    | 57 +++++++++++++++++++++++++++++++++++++-
 drivers/vfio/cdx/private.h |  2 ++
 2 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/cdx/main.c b/drivers/vfio/cdx/main.c
index c376a69d2db2..53ed8e6c499f 100644
--- a/drivers/vfio/cdx/main.c
+++ b/drivers/vfio/cdx/main.c
@@ -14,7 +14,7 @@ static int vfio_cdx_open_device(struct vfio_device *core_vdev)
 		container_of(core_vdev, struct vfio_cdx_device, vdev);
 	struct cdx_device *cdx_dev = to_cdx_device(core_vdev->dev);
 	int count = cdx_dev->res_count;
-	int i;
+	int i, ret;
 
 	vdev->regions = kcalloc(count, sizeof(struct vfio_cdx_region),
 				GFP_KERNEL_ACCOUNT);
@@ -39,6 +39,17 @@ static int vfio_cdx_open_device(struct vfio_device *core_vdev)
 		if (!(cdx_dev->res[i].flags & IORESOURCE_READONLY))
 			vdev->regions[i].flags |= VFIO_REGION_INFO_FLAG_WRITE;
 	}
+	ret = cdx_dev_reset(core_vdev->dev);
+	if (ret) {
+		kfree(vdev->regions);
+		vdev->regions = NULL;
+		return ret;
+	}
+	ret = cdx_clear_master(cdx_dev);
+	if (ret)
+		vdev->flags &= ~BME_SUPPORT;
+	else
+		vdev->flags |= BME_SUPPORT;
 
 	return 0;
 }
@@ -52,6 +63,49 @@ static void vfio_cdx_close_device(struct vfio_device *core_vdev)
 	cdx_dev_reset(core_vdev->dev);
 }
 
+static int vfio_cdx_bm_ctrl(struct vfio_device *core_vdev, u32 flags,
+			    void __user *arg, size_t argsz)
+{
+	size_t minsz =
+		offsetofend(struct vfio_device_feature_bus_master, op);
+	struct vfio_cdx_device *vdev =
+		container_of(core_vdev, struct vfio_cdx_device, vdev);
+	struct cdx_device *cdx_dev = to_cdx_device(core_vdev->dev);
+	struct vfio_device_feature_bus_master ops;
+	int ret;
+
+	if (!vdev->flags & BME_SUPPORT)
+		return -ENOTTY;
+
+	ret = vfio_check_feature(flags, argsz, VFIO_DEVICE_FEATURE_SET,
+				 sizeof(ops));
+	if (ret != 1)
+		return ret;
+
+	if (copy_from_user(&ops, arg, minsz))
+		return -EFAULT;
+
+	switch (ops.op) {
+	case VFIO_DEVICE_FEATURE_CLEAR_MASTER:
+		return cdx_clear_master(cdx_dev);
+	case VFIO_DEVICE_FEATURE_SET_MASTER:
+		return cdx_set_master(cdx_dev);
+	default:
+		return -EINVAL;
+	}
+}
+
+static int vfio_cdx_ioctl_feature(struct vfio_device *device, u32 flags,
+				  void __user *arg, size_t argsz)
+{
+	switch (flags & VFIO_DEVICE_FEATURE_MASK) {
+	case VFIO_DEVICE_FEATURE_BUS_MASTER:
+		return vfio_cdx_bm_ctrl(device, flags, arg, argsz);
+	default:
+		return -ENOTTY;
+	}
+}
+
 static int vfio_cdx_ioctl_get_info(struct vfio_cdx_device *vdev,
 				   struct vfio_device_info __user *arg)
 {
@@ -169,6 +223,7 @@ static const struct vfio_device_ops vfio_cdx_ops = {
 	.open_device	= vfio_cdx_open_device,
 	.close_device	= vfio_cdx_close_device,
 	.ioctl		= vfio_cdx_ioctl,
+	.device_feature = vfio_cdx_ioctl_feature,
 	.mmap		= vfio_cdx_mmap,
 	.bind_iommufd	= vfio_iommufd_physical_bind,
 	.unbind_iommufd	= vfio_iommufd_physical_unbind,
diff --git a/drivers/vfio/cdx/private.h b/drivers/vfio/cdx/private.h
index 8bdc117ea88e..8e9d25913728 100644
--- a/drivers/vfio/cdx/private.h
+++ b/drivers/vfio/cdx/private.h
@@ -23,6 +23,8 @@ struct vfio_cdx_region {
 struct vfio_cdx_device {
 	struct vfio_device	vdev;
 	struct vfio_cdx_region	*regions;
+	u32			flags;
+#define BME_SUPPORT BIT(0)
 };
 
 #endif /* VFIO_CDX_PRIVATE_H */
-- 
2.17.1