netdev - Re: [PATCH net] hv_netvsc: Fix race between VF offering and VF association message from host

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Date:   Thu, 29 Sep 2022 19:26:20 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Gaurav Kohli <gauravkohli@...ux.microsoft.com>
Cc:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        wei.liu@...nel.org, decui@...rosoft.com,
        linux-hyperv@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net] hv_netvsc: Fix race between VF offering and VF
 association message from host

On Wed, 28 Sep 2022 06:48:33 -0700 Gaurav Kohli wrote:
> During vm boot, there might be possibility that vf registration
> call comes before the vf association from host to vm.
> 
> And this might break netvsc vf path, To prevent the same block
> vf registration until vf bind message comes from host.
> 
> Cc: stable@...r.kernel.org
> Fixes: 00d7ddba11436 ("hv_netvsc: pair VF based on serial number")
> Signed-off-by: Gaurav Kohli <gauravkohli@...ux.microsoft.com>

Is it possible to add a timeout or such? Waiting for an external 
event while holding rtnl lock seems a little scary.

The other question is - what protects the completion and ->vf_alloc
from races? Is there some locking? ->vf_alloc only goes from 0 to 1
and never back?