ACK/Cmnt: [focal:linux-azure][LP:#1894896][PATCH] hv_netvsc: Fix hibernation for mlx5 VF driver

[Stefan Bader]

On 28.10.20 13:05, Marcelo Henrique Cerri wrote:
> On Wed, Oct 28, 2020 at 09:43:11AM +0100, Stefan Bader wrote:
>> On 27.10.20 18:18, Marcelo Henrique Cerri wrote:
>>> From: Dexuan Cui <decui at microsoft.com>
>>>
>>> BugLink: https://bugs.launchpad.net/bugs/1894896
>>>
>>> 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 <decui at microsoft.com>
>>> Signed-off-by: Jakub Kicinski <kuba at kernel.org>
>>> (cherry picked from commit 19162fd4063a3211843b997a454b505edb81d5ce)
>>> Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri at canonical.com>
>> Acked-by: Stefan Bader <stefan.bader at canonical.com>
>>> ---
>>
>> Just two notes not related to the patch itself. One just for whoever applies it
>> later. Maybe no longer an issue but I remember some issues with the cutoff hints
>> when there are multiple of them. I would maybe manually delete things from the
>> downloaded patch...
>> Second is about the primary tasks on launchpad. This always relates to the
>> current development series and is a moving target. Right now, there would be no
>> source for azure there, so that task should be invalid. The reason for not
>> leaving around any tasks in an open (new, confirmed, triaged, in progress) state
>> is that this prevents the bug report from considered done. So it still shows up
>> in bug searches and is counted as "active" bug. And there is already enough of
>> those.
> 
> Thanks for the explanation, Stefan. What issue did you have with the
> cutoff hints? Was the comment after the three dashed included to the
> commit message?

Yes, either all or one of them or not at all being happy on git am. But again,
it has been a long while ago. So its just a vague reminder to double check.


> 
> 
>>
>> -Stefan
>>
>>>
>>> Marcelo's comments:
>>>
>>> I was able to reproduce the problem with the current version from
>>> focal-updates following the test instructions from the LP bug and I
>>> was also able to confirm the fix solves the problem with a test
>>> kernel:
>>>
>>> https://kernel.ubuntu.com/~mhcerri/azure/focal-linux-azure_lp1894896.tgz
>>>
>>> 5.8 already received the fix via an upstream stable update
>>> (LP:#1894896) and hibernation is not supported in 4.15 linux-azure.
>>>
>>> Besides that the fix is a clean cherry-pick from upstream.
>>>
>>> ---
>>>  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 33d9d17ee0e0..be5ede2a6b94 100644
>>> --- a/drivers/net/hyperv/netvsc_drv.c
>>> +++ b/drivers/net/hyperv/netvsc_drv.c
>>> @@ -2551,8 +2551,8 @@ 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);
>>> @@ -2568,10 +2568,6 @@ 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);
>>>  
>>> @@ -2587,6 +2583,7 @@ 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();
>>> @@ -2599,6 +2596,15 @@ 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;
>>> +
>>>  	rtnl_unlock();
>>>  
>>>  	return ret;
>>>
>>
>>
> 
> 
> 
> 


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