Signed-off-by: Juan Quintela <quintela@redhat.com>
---
 migration/options.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/migration/options.c b/migration/options.c
index b62ab30cd5..c6674a4753 100644
--- a/migration/options.c
+++ b/migration/options.c
@@ -547,6 +547,13 @@ bool migrate_caps_check(bool *old_caps, bool *new_caps, Error **errp)
         }
     }
 
+    if (new_caps[MIGRATION_CAPABILITY_MULTIFD]) {
+        if (new_caps[MIGRATION_CAPABILITY_XBZRLE]) {
+            error_setg(errp, "Multifd is not compatible with xbzrle");
+            return false;
+        }
+    }
+
     return true;
 }
 
-- 
2.40.1

On Tue, 13 Jun 2023 16:57:40 +0200
Juan Quintela <quintela@redhat.com> wrote:

> Signed-off-by: Juan Quintela <quintela@redhat.com>
> ---
>  migration/options.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/migration/options.c b/migration/options.c
> index b62ab30cd5..c6674a4753 100644
> --- a/migration/options.c
> +++ b/migration/options.c
> @@ -547,6 +547,13 @@ bool migrate_caps_check(bool *old_caps, bool *new_caps, Error **errp)
>          }
>      }
>  
> +    if (new_caps[MIGRATION_CAPABILITY_MULTIFD]) {
> +        if (new_caps[MIGRATION_CAPABILITY_XBZRLE]) {
> +            error_setg(errp, "Multifd is not compatible with xbzrle");
> +            return false;
> +        }
> +    }
> +
>      return true;
>  }
>  

Hmm, I think supporting xbzrle + multifd might be worthwhile as an
alternative to xbzrle + compress.
I don't use it, but it should be easy to do by just letting xbzlre try
to handle the page before multifd. 
There shouldn't be any incompatibilities other than that, as long as
xbzlre sees the pages before multifd and the zero-page case is still
handled the old way.

Best Regards,
Lukas Straub

Lukas Straub <lukasstraub2@web.de> wrote:
> On Tue, 13 Jun 2023 16:57:40 +0200
> Juan Quintela <quintela@redhat.com> wrote:
>
>> Signed-off-by: Juan Quintela <quintela@redhat.com>
>> ---
>>  migration/options.c | 7 +++++++
>>  1 file changed, 7 insertions(+)
>> 
>> diff --git a/migration/options.c b/migration/options.c
>> index b62ab30cd5..c6674a4753 100644
>> --- a/migration/options.c
>> +++ b/migration/options.c
>> @@ -547,6 +547,13 @@ bool migrate_caps_check(bool *old_caps, bool *new_caps, Error **errp)
>>          }
>>      }
>>  
>> +    if (new_caps[MIGRATION_CAPABILITY_MULTIFD]) {
>> +        if (new_caps[MIGRATION_CAPABILITY_XBZRLE]) {
>> +            error_setg(errp, "Multifd is not compatible with xbzrle");
>> +            return false;
>> +        }
>> +    }
>> +
>>      return true;
>>  }
>>  
>
> Hmm, I think supporting xbzrle + multifd might be worthwhile as an
> alternative to xbzrle + compress.

Nack.

> I don't use it, but it should be easy to do by just letting xbzlre try
> to handle the page before multifd.

My idea here is to implement xbzrle as we implement zlib/zstd on
multifd.  Just go from there.

> There shouldn't be any incompatibilities other than that, as long as
> xbzlre sees the pages before multifd and the zero-page case is still
> handled the old way.

The way that I say is going to be easier and probably also faster.

Later, Juan.