[v2,1/1] migration: Disable postcopy + multifd migration

Commit Message

Leonardo Bras April 25, 2023, 3:33 a.m. UTC

Since the introduction of multifd, it's possible to perform a multifd
migration and finish it using postcopy.

A bug introduced by yank (fixed on cfc3bcf373) was previously preventing
a successful use of this migration scenario, and now thing should be
working on most scenarios.

But since there is not enough testing/support nor any reported users for
this scenario, we should disable this combination before it may cause any
problems for users.

Suggested-by: Dr. David Alan Gilbert <[e-mail]>
Signed-off-by: Leonardo Bras <[e-mail]>
Acked-by: Peter Xu <[e-mail]>
Reviewed-by: Dr. David Alan Gilbert <[e-mail]>
---
Changes since RFC:
- Updated to latest master branch
- Included Acks and Reviews

 migration/options.c | 5 +++++
 1 file changed, 5 insertions(+)

Comments

Juan Quintela April 25, 2023, 7:22 a.m. UTC | #1

Leonardo Bras <[e-mail]> wrote:
> Since the introduction of multifd, it's possible to perform a multifd
> migration and finish it using postcopy.
>
> A bug introduced by yank (fixed on cfc3bcf373) was previously preventing
> a successful use of this migration scenario, and now thing should be
> working on most scenarios.
>
> But since there is not enough testing/support nor any reported users for
> this scenario, we should disable this combination before it may cause any
> problems for users.
>
> Suggested-by: Dr. David Alan Gilbert <[e-mail]>
> Signed-off-by: Leonardo Bras <[e-mail]>
> Acked-by: Peter Xu <[e-mail]>
> Reviewed-by: Dr. David Alan Gilbert <[e-mail]>

Reviewed-by: Juan Quintela <[e-mail]>

queued.

Patch

diff --git a/migration/options.c b/migration/options.c
index 8e8753d9be..b0fc0aa60c 100644
--- a/migration/options.c
+++ b/migration/options.c
@@ -322,6 +322,11 @@  bool migrate_caps_check(bool *old_caps, bool *new_caps, Error **errp)
             error_setg(errp, "Postcopy is not compatible with ignore-shared");
             return false;
         }
+
+        if (cap_list[MIGRATION_CAPABILITY_MULTIFD]) {
+            error_setg(errp, "Postcopy is not yet compatible with multifd");
+            return false;
+        }
     }
 
     if (new_caps[MIGRATION_CAPABILITY_BACKGROUND_SNAPSHOT]) {