Re: [PATCH v3 2/2] migration: check magic value for deciding the mapping of channels

[Daniel P . Berrangé]

On Sat, Nov 19, 2022 at 09:36:15AM +0000, manish.mishra wrote:
> Current logic assumes that channel connections on the destination side are
> always established in the same order as the source and the first one will
> always be the main channel followed by the multifid or post-copy
> preemption channel. This may not be always true, as even if a channel has a
> connection established on the source side it can be in the pending state on
> the destination side and a newer connection can be established first.
> Basically causing out of order mapping of channels on the destination side.
> Currently, all channels except post-copy preempt send a magic number, this
> patch uses that magic number to decide the type of channel. This logic is
> applicable only for precopy(multifd) live migration, as mentioned, the
> post-copy preempt channel does not send any magic number. Also, tls live
> migrations already does tls handshake before creating other channels, so
> this issue is not possible with tls, hence this logic is avoided for tls
> live migrations. This patch uses read peek to check the magic number of
> channels so that current data/control stream management remains
> un-effected.
> 
> Suggested-by: Daniel P. Berrangé <berrange@redhat.com
> Signed-off-by: manish.mishra <manish.mishra@nutanix.com>
> ---
>  migration/migration.c    | 44 +++++++++++++++++++++++++++++-----------
>  migration/multifd.c      | 12 ++++-------
>  migration/multifd.h      |  2 +-
>  migration/postcopy-ram.c |  5 +----
>  migration/postcopy-ram.h |  2 +-
>  5 files changed, 39 insertions(+), 26 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

With regards,
Daniel
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