netdev - Re: [PATCH net] hv_netvsc: Fix hibernation for mlx5 VF driver

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Message-ID: <20200905162712.65b886a4@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Sat, 5 Sep 2020 16:27:12 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Dexuan Cui <decui@...rosoft.com>
Cc:     wei.liu@...nel.org, kys@...rosoft.com, haiyangz@...rosoft.com,
        sthemmin@...rosoft.com, davem@...emloft.net,
        linux-hyperv@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, mikelley@...rosoft.com
Subject: Re: [PATCH net] hv_netvsc: Fix hibernation for mlx5 VF driver

On Fri,  4 Sep 2020 19:52:18 -0700 Dexuan Cui wrote:
> mlx5_suspend()/resume() keep the network interface, so during hibernation
> netvsc_unregister_vf() and netvsc_register_vf() are not called, and hence
> netvsc_resume() should call netvsc_vf_changed() to switch the data path
> back to the VF after hibernation.

Does suspending the system automatically switch back to the synthetic
datapath? Please clarify this in the commit message and/or add a code
comment.

> Similarly, netvsc_suspend() should not call netvsc_unregister_vf().
> 
> BTW, mlx4_suspend()/resume() are differnt in that they destroy and
> re-create the network device, so netvsc_register_vf() and
> netvsc_unregister_vf() are automatically called. Note: mlx4 can also work
> with the changes here because in netvsc_suspend()/resume()
> ndev_ctx->vf_netdev is NULL for mlx4.
> 
> Fixes: 0efeea5fb153 ("hv_netvsc: Add the support of hibernation")
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> ---
>  drivers/net/hyperv/netvsc_drv.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
> index 64b0a74c1523..f896059a9588 100644
> --- a/drivers/net/hyperv/netvsc_drv.c
> +++ b/drivers/net/hyperv/netvsc_drv.c
> @@ -2587,7 +2587,7 @@ static int netvsc_remove(struct hv_device *dev)
>  static int netvsc_suspend(struct hv_device *dev)
>  {
>  	struct net_device_context *ndev_ctx;
> -	struct net_device *vf_netdev, *net;
> +	struct net_device *net;
>  	struct netvsc_device *nvdev;
>  	int ret;

Please keep reverse xmas tree variable ordering.

> @@ -2604,10 +2604,6 @@ static int netvsc_suspend(struct hv_device *dev)
>  		goto out;
>  	}
>  
> -	vf_netdev = rtnl_dereference(ndev_ctx->vf_netdev);
> -	if (vf_netdev)
> -		netvsc_unregister_vf(vf_netdev);
> -
>  	/* Save the current config info */
>  	ndev_ctx->saved_netvsc_dev_info = netvsc_devinfo_get(nvdev);
>  
> @@ -2623,6 +2619,7 @@ static int netvsc_resume(struct hv_device *dev)
>  	struct net_device *net = hv_get_drvdata(dev);
>  	struct net_device_context *net_device_ctx;
>  	struct netvsc_device_info *device_info;
> +	struct net_device *vf_netdev;
>  	int ret;
>  
>  	rtnl_lock();
> @@ -2635,6 +2632,10 @@ static int netvsc_resume(struct hv_device *dev)
>  	netvsc_devinfo_put(device_info);
>  	net_device_ctx->saved_netvsc_dev_info = NULL;
>  
> +	vf_netdev = rtnl_dereference(net_device_ctx->vf_netdev);
> +	if (vf_netdev && netvsc_vf_changed(vf_netdev) != NOTIFY_OK)
> +		ret = -EINVAL;

Should you perhaps remove the VF in case of the failure?

>  	rtnl_unlock();
>  
>  	return ret;