Re: [PATCH v2 6/7] vdpa/mlx5: conditionally show MTU and STATUS in config space

[Si-Wei Liu]

On 2/3/2023 12:14 AM, Michael S. Tsirkin wrote:
> On Tue, Jan 31, 2023 at 03:22:24PM -0800, Si-Wei Liu wrote:
> > The spec says:
> >      mtu only exists if VIRTIO_NET_F_MTU is set
> >      status only exists if VIRTIO_NET_F_STATUS is set
> >
> > We should only show MTU and STATUS conditionally depending on
> > the feature bits.
> >
> > Signed-off-by: Si-Wei Liu <si-wei.liu@xxxxxxxxxx>
> so change the subject pls. it seems to say you are showing them
> when you previously didn't, what's going on is something like:
>
> 	make MTU/status access conditional on feature bits
I ever considered something similar as I wrote it, but there's no actual 
config space access involved, and what the code is doing is to prohibit 
*presenting* the related field to config space subject to feature bit. 
So maybe this is more accurate?

make MTU/status presence conditional on feature bits

Thanks,
-Siwei
> > ---
> >   drivers/vdpa/mlx5/net/mlx5_vnet.c | 22 ++++++++++++++--------
> >   1 file changed, 14 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > index 3a6dbbc6..3d49eae 100644
> > --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > @@ -3009,6 +3009,8 @@ static int event_handler(struct notifier_block *nb, unsigned long event, void *p
> >   	struct mlx5_vdpa_wq_ent *wqent;
> >   
> >   	if (event == MLX5_EVENT_TYPE_PORT_CHANGE) {
> > +		if (!(ndev->mvdev.actual_features & BIT_ULL(VIRTIO_NET_F_STATUS)))
> > +			return NOTIFY_DONE;
> >   		switch (eqe->sub_type) {
> >   		case MLX5_PORT_CHANGE_SUBTYPE_DOWN:
> >   		case MLX5_PORT_CHANGE_SUBTYPE_ACTIVE:
> > @@ -3118,16 +3120,20 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name,
> >   			goto err_alloc;
> >   	}
> >   
> > -	err = query_mtu(mdev, &mtu);
> > -	if (err)
> > -		goto err_alloc;
> > +	if (device_features & BIT_ULL(VIRTIO_NET_F_MTU)) {
> > +		err = query_mtu(mdev, &mtu);
> > +		if (err)
> > +			goto err_alloc;
> >   
> > -	ndev->config.mtu = cpu_to_mlx5vdpa16(mvdev, mtu);
> > +		ndev->config.mtu = cpu_to_mlx5vdpa16(mvdev, mtu);
> > +	}
> >   
> > -	if (get_link_state(mvdev))
> > -		ndev->config.status |= cpu_to_mlx5vdpa16(mvdev, VIRTIO_NET_S_LINK_UP);
> > -	else
> > -		ndev->config.status &= cpu_to_mlx5vdpa16(mvdev, ~VIRTIO_NET_S_LINK_UP);
> > +	if (device_features & BIT_ULL(VIRTIO_NET_F_STATUS)) {
> > +		if (get_link_state(mvdev))
> > +			ndev->config.status |= cpu_to_mlx5vdpa16(mvdev, VIRTIO_NET_S_LINK_UP);
> > +		else
> > +			ndev->config.status &= cpu_to_mlx5vdpa16(mvdev, ~VIRTIO_NET_S_LINK_UP);
> > +	}
> >   
> >   	if (add_config->mask & (1 << VDPA_ATTR_DEV_NET_CFG_MACADDR)) {
> >   		memcpy(ndev->config.mac, add_config->net.mac, ETH_ALEN);
> > --
> > 1.8.3.1