Re: [PATCH v2 07/16] migration: Introduce stopcopy_bytes in save_query_pending()

[Juraj Marcin <jmarcin@redhat.com>]

On 2026-04-21 16:21, Peter Xu wrote:
> Allow modules to report data that can only be migrated after VM is stopped.
> 
> When this concept is introduced, we will need to account stopcopy size to
> be part of pending_size as before.
> 
> However, when there're data only can be migrated in stopcopy phase, it
> means the old "pending_size" may not always be able to reach low enough to
> kickoff an slow version of query sync.
> 
> It used to be almost guaranteed to happen as all prior iterative modules
> doesn't have stopcopy only data.  VFIO may change that fact by having some
> data that must be copied during stop phase.
> 
> So we need to make sure QEMU will kickoff a synchronized version of query
> pending when all precopy data is migrated.  This might be important to VFIO
> to keep making progress even if the downtime cannot yet be satisfied.
> 
> So far, this patch should introduce no functional change, as no module yet
> report stopcopy size.
> 
> This paves way for VFIO to properly report its pending data sizes, which
> will start to include stop-only data.
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  include/migration/register.h |  7 ++++
>  migration/migration.c        | 65 ++++++++++++++++++++++++++++++------
>  migration/savevm.c           | 10 ++++--
>  migration/trace-events       |  2 +-
>  4 files changed, 70 insertions(+), 14 deletions(-)

Reviewed-by: Juraj Marcin <jmarcin@redhat.com>