On Tue, Sep 13, 2022 at 5:21 AM David Marchand
<[email protected]> wrote:
>
> At some point in OVS history, some virtio features were announced as
> supported (ECN and UFO virtio features).
>
> The userspace TSO code, which has been added later, does not support
> those features and tries to disable them.
>
> This breaks OVS upgrades: if an existing VM already negotiated such
> features, their lack on reconnection to an upgraded OVS triggers a
> vhost socket disconnection by Qemu.
> This results in an endless loop because Qemu then retries with the same
> set of virtio features.
>
> This patch proposes to try and detect those vhost socket disconnection
> and fallback restoring the old virtio features (and disabling TSO for this
> vhost port).
>
> Signed-off-by: David Marchand <[email protected]>
> ---
> Changelog since v1:
> - added a note in the documentation,
> - fixed vhost unregister trigger (so that both disabling and re-enabling
>   TSO is handled),
> - cleared netdev features when disabling TSO,
> - changed level and ratelimited log message on vhost socket disconnect,
>

This does solve the issue. My only real comment is it may be opaque to
an end user. Do you think it makes sense to add this information to
netdev_dpdk_vhost_user_get_status? Or do you think the log message
should suffice?


Cheers,
M

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