From afed4273b5c9438dfbaa0b4762d0433f295ccdc1 Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Tue, 4 Oct 2022 14:24:28 -0400 Subject: migration: Disallow postcopy preempt to be used with compress The preempt mode requires the capability to assign channel for each of the page, while the compression logic will currently assign pages to different compress thread/local-channel so potentially they're incompatible. Reviewed-by: Dr. David Alan Gilbert Signed-off-by: Peter Xu Reviewed-by: Juan Quintela Signed-off-by: Juan Quintela --- migration/migration.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/migration/migration.c b/migration/migration.c index 739bb683f3..f3ed77a7d0 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -1337,6 +1337,17 @@ static bool migrate_caps_check(bool *cap_list, error_setg(errp, "Postcopy preempt requires postcopy-ram"); return false; } + + /* + * Preempt mode requires urgent pages to be sent in separate + * channel, OTOH compression logic will disorder all pages into + * different compression channels, which is not compatible with the + * preempt assumptions on channel assignments. + */ + if (cap_list[MIGRATION_CAPABILITY_COMPRESS]) { + error_setg(errp, "Postcopy preempt not compatible with compress"); + return false; + } } return true; -- cgit v1.2.3-55-g7522