On Tue, Feb 03, 2026 at 11:15:09AM +0100, Lukas Straub wrote:
> Since
> 121ccedc2b migration: block incoming colo when capability is disabled
>
> x-colo capability needs to be always enabled on the incoming side.
> So migration_incoming_colo_enabled() and migrate_colo() are equivalent
> with migrate_colo() being easier to reason about since it is always true
> during the whole migration.
>
> Use migrate_colo() to initialize the ram cache in the normal migration path.
>
> Reviewed-by: Fabiano Rosas <farosas@suse.de>
> Signed-off-by: Lukas Straub <lukasstraub2@web.de>
Since the goal of this patch is to drop the COLO migration command, this
looks an improvement indeed,
Reviewed-by: Peter Xu <peterx@redhat.com>
I'll still comment though for possible future updates..
> ---
> migration/migration.c | 18 ++++++++++++++----
> migration/savevm.c | 14 +-------------
> 2 files changed, 15 insertions(+), 17 deletions(-)
>
> diff --git a/migration/migration.c b/migration/migration.c
> index b103a82fc0b83009d01d238ff16c0a542d83509f..a73d842ad8b060dc84273ade36ef7dc8b87421f3 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -630,10 +630,6 @@ int migration_incoming_enable_colo(Error **errp)
> return -EINVAL;
> }
>
> - if (ram_block_discard_disable(true)) {
> - error_setg(errp, "COLO: cannot disable RAM discard");
> - return -EBUSY;
> - }
> migration_colo_enabled = true;
> return 0;
> }
> @@ -770,6 +766,20 @@ process_incoming_migration_co(void *opaque)
>
> assert(mis->from_src_file);
>
> + if (migrate_colo()) {
> + if (ram_block_discard_disable(true)) {
IMHO this is something we could have done at migrate_incoming and fail the
QMP command directly, rather than waiting until this late.
> + error_setg(&local_err, "COLO: cannot disable RAM discard");
> + goto fail;
> + }
> +
> + ret = colo_init_ram_cache(&local_err);
This might be more suitable to be put in ram's load_setup() (which should
happen at the initial migration phase, before colo taking snapshots), then
I believe this function can be unexported too.
> + if (ret) {
> + error_prepend(&local_err, "failed to init colo RAM cache: %d: ",
> + ret);
> + goto fail;
> + }
> + }
> +
> mis->largest_page_size = qemu_ram_pagesize_largest();
> postcopy_state_set(POSTCOPY_INCOMING_NONE);
> migrate_set_state(&mis->state, MIGRATION_STATUS_SETUP,
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 3dc812a7bbb4e8f5321114c9919d4619798fed5e..0353ac2d0de819b6547a1f771e6a4c3b8fb1e4ef 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2407,19 +2407,7 @@ static int loadvm_process_enable_colo(MigrationIncomingState *mis,
> Error **errp)
> {
> ERRP_GUARD();
> - int ret;
> -
> - ret = migration_incoming_enable_colo(errp);
> - if (ret < 0) {
> - return ret;
> - }
> -
> - ret = colo_init_ram_cache(errp);
> - if (ret) {
> - error_prepend(errp, "failed to init colo RAM cache: %d: ", ret);
> - migration_incoming_disable_colo();
> - }
> - return ret;
> + return migration_incoming_enable_colo(errp);
> }
>
> static int loadvm_postcopy_handle_switchover_start(Error **errp)
>
> --
> 2.39.5
>
--
Peter Xu