netdev - Re: [PATCH net 2/4] ice: Stop processing VF messages during teardown

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Message-ID: <20210809155838.208796aa@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Mon, 9 Aug 2021 15:58:38 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Tony Nguyen <anthony.l.nguyen@...el.com>
Cc:     davem@...emloft.net,
        Anirudh Venkataramanan <anirudh.venkataramanan@...el.com>,
        netdev@...r.kernel.org,
        Konrad Jankowski <konrad0.jankowski@...el.com>
Subject: Re: [PATCH net 2/4] ice: Stop processing VF messages during
 teardown

On Mon,  9 Aug 2021 10:14:00 -0700 Tony Nguyen wrote:
> When VFs are setup and torn down in quick succession, it is possible
> that a VF is torn down by the PF while the VF's virtchnl requests are
> still in the PF's mailbox ring. Processing the VF's virtchnl request
> when the VF itself doesn't exist results in undefined behavior. Fix
> this by adding a check to stop processing virtchnl requests when VF
> teardown is in progress.

What is "undefined behavior" in this context? Please improve the commit
message. It should describe misbehavior visible to the user, failing
that what will happen from kernel/device perspective. Or state that it's
just a "fix" to align with some internal driver <> firmware spec...