On Tue, Nov 16, 2021 at 05:34:50PM +0100, Juan Quintela wrote:
> Daniel P. Berrangé <berra...@redhat.com> wrote:
>
> >>
> >> if (params->zerocopy &&
> >> (params->parameters.multifd_compression !=
> >> MULTIFD_COMPRESSION_NONE ||
> >> migrate_use_tls())) {
> >> error_setg(&err,
> >> "Zerocopy only available for non-compressed non-TLS
> >> multifd migration");
> >> return false;
> >> }
> >>
> >> You have to do the equivalent of multifd_compression and tls enablement,
> >> to see that zerocopy is not enabled, of course.
> >>
> >> I would prefer to check for QIO_CHANNEL_FEATUR_WRITE_ZEROCPY there, but
> >> I can't see a way of doing that without a qio.
> >
> > I don't think you need to check that feature flag.
>
> Oh, I mean other thing.
>
> When you set "zerocopy" capability, you don't know if the kernel support
> it. My understanding is that the only way to check if it supported is
> here.
If you reqest it and it isn't supported you'll get an error back from
qio_channel_writev_zerocopy(). That's a bit too late though.
Ideally we should report an error straight after the migration code
creates the I/O channel, by querying for the feature.
Regards,
Daniel
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