Before loading the guest states, ensure that the preempt channel has been ready to use, as some of the states (e.g. via virtio_load) might trigger page faults that will be handled through the preempt channel. So yield to the main thread in the case that the channel create event has been dispatched.
Originally-by: Lei Wang <lei4.w...@intel.com> Link: https://lore.kernel.org/all/9aa5d1be-7801-40dd-83fd-f7e041ced...@intel.com/T/ Suggested-by: Peter Xu <pet...@redhat.com> Signed-off-by: Lei Wang <lei4.w...@intel.com> Signed-off-by: Wei Wang <wei.w.w...@intel.com> --- migration/savevm.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/migration/savevm.c b/migration/savevm.c index 388d7af7cd..fbc9f2bdd4 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -2342,6 +2342,23 @@ static int loadvm_handle_cmd_packaged(MigrationIncomingState *mis) QEMUFile *packf = qemu_file_new_input(QIO_CHANNEL(bioc)); + /* + * Before loading the guest states, ensure that the preempt channel has + * been ready to use, as some of the states (e.g. via virtio_load) might + * trigger page faults that will be handled through the preempt channel. + * So yield to the main thread in the case that the channel create event + * has been dispatched. + */ + do { + if (!migrate_postcopy_preempt() || !qemu_in_coroutine() || + mis->postcopy_qemufile_dst) { + break; + } + + aio_co_schedule(qemu_get_current_aio_context(), qemu_coroutine_self()); + qemu_coroutine_yield(); + } while (!qemu_sem_timedwait(&mis->postcopy_qemufile_dst_done, 1)); + ret = qemu_loadvm_state_main(packf, mis); trace_loadvm_handle_cmd_packaged_main(ret); qemu_fclose(packf); -- 2.27.0
