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Date:   Thu, 29 Sep 2022 19:26:20 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     Gaurav Kohli <gauravkohli@linux.microsoft.com>
Cc:     kys@microsoft.com, haiyangz@microsoft.com, sthemmin@microsoft.com,
        wei.liu@kernel.org, decui@microsoft.com,
        linux-hyperv@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH net] hv_netvsc: Fix race between VF offering and VF
 association message from host
Message-ID: <20220929192620.2fa1542f@kernel.org>
In-Reply-To: <1664372913-26140-1-git-send-email-gauravkohli@linux.microsoft.com>
References: <1664372913-26140-1-git-send-email-gauravkohli@linux.microsoft.com>
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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@vger.kernel.org
> Fixes: 00d7ddba11436 ("hv_netvsc: pair VF based on serial number")
> Signed-off-by: Gaurav Kohli <gauravkohli@linux.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?