[PATCH 2/3] vdpa/mlx5: set_features should nack MQ if no CTRL_VQ

[Si-Wei Liu <si-wei.liu@oracle.com>]

Made corresponding change per spec:

The device MUST NOT offer a feature which requires another feature
which was not offered.

Fixes: 52893733f2c5 ("vdpa/mlx5: Add multiqueue support")
Signed-off-by: Si-Wei Liu<si-wei.liu@oracle.com>
---
 drivers/vdpa/mlx5/net/mlx5_vnet.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index b53603d..46d4deb 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -1897,11 +1897,21 @@ static u64 mlx5_vdpa_get_device_features(struct vdpa_device *vdev)
 	return ndev->mvdev.mlx_features;
 }
 
-static int verify_min_features(struct mlx5_vdpa_dev *mvdev, u64 features)
+static int verify_driver_features(struct mlx5_vdpa_dev *mvdev, u64 *features)
 {
-	if (!(features & BIT_ULL(VIRTIO_F_ACCESS_PLATFORM)))
+	/* minimum features to expect */
+	if (!(*features & BIT_ULL(VIRTIO_F_ACCESS_PLATFORM)))
 		return -EOPNOTSUPP;
 
+	/* Double check features combination sent down by the driver.
+	 * NACK invalid feature due to the absence of depended feature.
+	 * Driver is expected to re-read the negotiated features once
+	 * return from set_driver_features.
+	 */
+	if ((*features & (BIT_ULL(VIRTIO_NET_F_MQ) | BIT_ULL(VIRTIO_NET_F_CTRL_VQ))) ==
+            BIT_ULL(VIRTIO_NET_F_MQ))
+		*features &= ~BIT_ULL(VIRTIO_NET_F_MQ);
+
 	return 0;
 }
 
@@ -1977,7 +1987,7 @@ static int mlx5_vdpa_set_driver_features(struct vdpa_device *vdev, u64 features)
 
 	print_features(mvdev, features, true);
 
-	err = verify_min_features(mvdev, features);
+	err = verify_driver_features(mvdev, &features);
 	if (err)
 		return err;
 
-- 
1.8.3.1

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