Re: [PATCH v5 6/6] multifd: Implement zerocopy write in multifd migration (multifd-zerocopy)

[Juan Quintela]

Daniel P. Berrangé <berrange@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.

I agree with the rest of the arguments.

Later, Juan.