Re: [PATCH v2] vdpa/mlx5: Fix mlx5_vdpa_get_config() endianness on big-endian machines

[Dragos Tatulea]

On 02/04, Konstantin Shkolnyy wrote:
> mlx5_vdpa_dev_add() doesn’t initialize mvdev->actual_features. It’s
> initialized later by mlx5_vdpa_set_driver_features(). However,
> mlx5_vdpa_get_config() depends on the VIRTIO_F_VERSION_1 flag in
> actual_features, to return data with correct endianness. When it’s called
> before mlx5_vdpa_set_driver_features(), the data are incorrectly returned
> as big-endian on big-endian machines, while QEMU then interprets them as
> little-endian.
> 
> The fix is to initialize this VIRTIO_F_VERSION_1 as early as possible,
> especially considering that mlx5_vdpa_dev_add() insists on this flag to
> always be set anyway.
> 
> Signed-off-by: Konstantin Shkolnyy <kshk@xxxxxxxxxxxxx>
> ---
> Changes in V2: Initialize only VIRTIO_F_VERSION_1 in actual_features,
> rather than all flags.
> 
>  drivers/vdpa/mlx5/net/mlx5_vnet.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 36099047560d..cccc49a08a1a 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -3884,6 +3884,9 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name,
>  	ndev->mvdev.max_vqs = max_vqs;
>  	mvdev = &ndev->mvdev;
>  	mvdev->mdev = mdev;
> +	/* cpu_to_mlx5vdpa16() below depends on this flag */
> +	mvdev->actual_features =
> +			(device_features & BIT_ULL(VIRTIO_F_VERSION_1));
>  
>  	ndev->vqs = kcalloc(max_vqs, sizeof(*ndev->vqs), GFP_KERNEL);
>  	ndev->event_cbs = kcalloc(max_vqs + 1, sizeof(*ndev->event_cbs), GFP_KERNEL);
> -- 
> 2.34.1
>
The patch looks good now. Thanks!

Reviewed-by: Dragos Tatulea <dtatulea@xxxxxxxxxx>