vdpa/mlx5: Fix queue type selection logic

get_queue_type() comments that splict virtqueue is preferred, however,
the actual logic preferred packed virtqueues. Since firmware has not
supported packed virtqueues we ended up using split virtqueues as was
desired.

Since we do not advertise support for packed virtqueues, we add a check
to verify split virtqueues are indeed supported.

Fixes: 1a86b377 ("vdpa/mlx5: Add VDPA driver for supported mlx5 devices")
Signed-off-by: Eli Cohen <elic@nvidia.com>
Link: https://lore.kernel.org/r/20210811053759.66752-1-elic@nvidia.comSigned-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/mlx5/net/mlx5_vnet.c

@@ -753,12 +753,12 @@ static int get_queue_type(struct mlx5_vdpa_net *ndev)
 	type_mask = MLX5_CAP_DEV_VDPA_EMULATION(ndev->mvdev.mdev, virtio_queue_type);
 
 	/* prefer split queue */
-	if (type_mask & MLX5_VIRTIO_EMULATION_CAP_VIRTIO_QUEUE_TYPE_PACKED)
-		return MLX5_VIRTIO_EMULATION_VIRTIO_QUEUE_TYPE_PACKED;
+	if (type_mask & MLX5_VIRTIO_EMULATION_CAP_VIRTIO_QUEUE_TYPE_SPLIT)
+		return MLX5_VIRTIO_EMULATION_VIRTIO_QUEUE_TYPE_SPLIT;
 
-	WARN_ON(!(type_mask & MLX5_VIRTIO_EMULATION_CAP_VIRTIO_QUEUE_TYPE_SPLIT));
+	WARN_ON(!(type_mask & MLX5_VIRTIO_EMULATION_CAP_VIRTIO_QUEUE_TYPE_PACKED));
 
-	return MLX5_VIRTIO_EMULATION_VIRTIO_QUEUE_TYPE_SPLIT;
+	return MLX5_VIRTIO_EMULATION_VIRTIO_QUEUE_TYPE_PACKED;
 }
 
 static bool vq_is_tx(u16 idx)
@@ -2030,6 +2030,12 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name)
 		return -ENOSPC;
 
 	mdev = mgtdev->madev->mdev;
+	if (!(MLX5_CAP_DEV_VDPA_EMULATION(mdev, virtio_queue_type) &
+	    MLX5_VIRTIO_EMULATION_CAP_VIRTIO_QUEUE_TYPE_SPLIT)) {
+		dev_warn(mdev->device, "missing support for split virtqueues\n");
+		return -EOPNOTSUPP;
+	}
+
 	/* we save one virtqueue for control virtqueue should we require it */
 	max_vqs = MLX5_CAP_DEV_VDPA_EMULATION(mdev, max_num_virtio_queues);
 	max_vqs = min_t(u32, max_vqs, MLX5_MAX_SUPPORTED_VQS);

include/linux/mlx5/mlx5_ifc_vdpa.h

@@ -11,13 +11,15 @@ enum {
 };
 
 enum {
-	MLX5_VIRTIO_EMULATION_CAP_VIRTIO_QUEUE_TYPE_SPLIT   = 0x1, // do I check this caps?
-	MLX5_VIRTIO_EMULATION_CAP_VIRTIO_QUEUE_TYPE_PACKED  = 0x2,
+	MLX5_VIRTIO_EMULATION_VIRTIO_QUEUE_TYPE_SPLIT   = 0,
+	MLX5_VIRTIO_EMULATION_VIRTIO_QUEUE_TYPE_PACKED  = 1,
 };
 
 enum {
-	MLX5_VIRTIO_EMULATION_VIRTIO_QUEUE_TYPE_SPLIT   = 0,
-	MLX5_VIRTIO_EMULATION_VIRTIO_QUEUE_TYPE_PACKED  = 1,
+	MLX5_VIRTIO_EMULATION_CAP_VIRTIO_QUEUE_TYPE_SPLIT =
+		BIT(MLX5_VIRTIO_EMULATION_VIRTIO_QUEUE_TYPE_SPLIT),
+	MLX5_VIRTIO_EMULATION_CAP_VIRTIO_QUEUE_TYPE_PACKED =
+		BIT(MLX5_VIRTIO_EMULATION_VIRTIO_QUEUE_TYPE_PACKED),
 };
 
 struct mlx5_ifc_virtio_q_bits {