From: Dexuan Cui <de...@microsoft.com> Sent: Monday, September 7, 2020 12:14 AM
>
> 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. Note: after we close and re-open the
> vmbus channel of the netvsc NIC in netvsc_suspend() and netvsc_resume(),
> the data path is implicitly switched to the netvsc NIC. Similarly,
> netvsc_suspend() should not call netvsc_unregister_vf(), otherwise the VF
> can no longer be used after hibernation.
>
> For mlx4, since the VF network interafce is explicitly destroyed and
> re-created during hibernation (see mlx4_suspend()/resume()), hv_netvsc
> already explicitly switches the data path from and to the VF automatically
> via netvsc_register_vf() and netvsc_unregister_vf(), so mlx4 doesn't need
> this fix. Note: mlx4 can still work with the fix 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 <de...@microsoft.com>
> ---
>
> Changes in v2 (Thanks Jakub Kicinski <k...@kernel.org>):
> Added coments in the changelog and the code about the implicit
> data path switching to the netvsc when we close/re-open the vmbus
> channels.
> Used reverse xmas order ordering in netvsc_remove().
>
> drivers/net/hyperv/netvsc_drv.c | 16 +++++++++++-----
> 1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
> index 64b0a74c1523..81c5c70b616a 100644
> --- a/drivers/net/hyperv/netvsc_drv.c
> +++ b/drivers/net/hyperv/netvsc_drv.c
> @@ -2587,8 +2587,8 @@ 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 netvsc_device *nvdev;
> + struct net_device *net;
> int ret;
>
> net = hv_get_drvdata(dev);
> @@ -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 +2632,15 @@ static int netvsc_resume(struct hv_device *dev)
> netvsc_devinfo_put(device_info);
> net_device_ctx->saved_netvsc_dev_info = NULL;
>
> + /* A NIC driver (e.g. mlx5) may keep the VF network interface across
> + * hibernation, but here the data path is implicitly switched to the
> + * netvsc NIC since the vmbus channel is closed and re-opened, so
> + * netvsc_vf_changed() must be used to switch the data path to the VF.
> + */
> + vf_netdev = rtnl_dereference(net_device_ctx->vf_netdev);
> + if (vf_netdev && netvsc_vf_changed(vf_netdev) != NOTIFY_OK)
> + ret = -EINVAL;
> +
I'm a little late looking at this code. But a question: Is it possible for
netvsc_resume() to be called before the VF driver's resume function
is called? If so, is it possible for netvsc_vf_changed() to find that the VF
is not up, and hence to switch the data path away from the VF instead of
to the VF?
Michael
> rtnl_unlock();
>
> return ret;
> --
> 2.19.1
