On Wed, Sep 20, 2023 at 05:04:11PM +0800, Li Zhijian wrote:
> From: Li Zhijian <lizhij...@cn.fujitsu.com>
>
> Destination will fail with:
> qemu-system-x86_64: rdma: Too many requests in this message
> (3638950032).Bailing.
>
> migrate with RDMA is different from tcp. RDMA has its own control
> message, and all traffic between RDMA_CONTROL_REGISTER_REQUEST and
> RDMA_CONTROL_REGISTER_FINISHED should not be disturbed.
>
> find_dirty_block() will be called during RDMA_CONTROL_REGISTER_REQUEST
> and RDMA_CONTROL_REGISTER_FINISHED, it will send a extra traffic to
> destination and cause migration to fail.
>
> Since there's no existing subroutine to indicate whether it's migrated
> by RDMA or not, and RDMA is not compatible with multifd, we use
> migrate_multifd() here.
>
> Fixes: 294e5a4034 ("multifd: Only flush once each full round of memory")
> Signed-off-by: Li Zhijian <lizhij...@cn.fujitsu.com>
> ---
> migration/ram.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index 9040d66e61..89ae28e21a 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -1399,7 +1399,8 @@ static int find_dirty_block(RAMState *rs,
> PageSearchStatus *pss)
> pss->page = 0;
> pss->block = QLIST_NEXT_RCU(pss->block, next);
> if (!pss->block) {
> - if (!migrate_multifd_flush_after_each_section()) {
> + if (migrate_multifd() &&
> + !migrate_multifd_flush_after_each_section()) {
> QEMUFile *f = rs->pss[RAM_CHANNEL_PRECOPY].pss_channel;
> int ret = multifd_send_sync_main(f);
> if (ret < 0) {
> --
> 2.31.1
>
Maybe better to put that check at the entry of
migrate_multifd_flush_after_each_section()?
I also hope that some day there's no multifd function called in generic
migration code paths..
--
Peter Xu
