From: Wei Wang <wei.w.w...@intel.com>
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 hasn't been
dispatched.
Cc: qemu-stable <qemu-sta...@nongnu.org>
Fixes: 9358982744 ("migration: Send requested page directly in rp-return
thread")
Originally-by: Lei Wang <lei4.w...@intel.com>
Link:
https://lore.kernel.org/all/9aa5d1be-7801-40dd-83fd-f7e041ced...@intel.com/T/
Signed-off-by: Lei Wang <lei4.w...@intel.com>
Signed-off-by: Wei Wang <wei.w.w...@intel.com>
Link: https://lore.kernel.org/r/20240405034056.23933-1-wei.w.w...@intel.com
[peterx: add a todo section, add Fixes and copy stable for 8.0+]
Signed-off-by: Peter Xu <pet...@redhat.com>
---
migration/savevm.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/migration/savevm.c b/migration/savevm.c
index 388d7af7cd..e7c1215671 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2342,6 +2342,27 @@ 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
+ * hasn't been dispatched.
+ *
+ * TODO: if we can move migration loadvm out of main thread, then we
+ * won't block main thread from polling the accept() fds. We can drop
+ * this as a whole when that is done.
+ */
+ 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 (1);
+
ret = qemu_loadvm_state_main(packf, mis);
trace_loadvm_handle_cmd_packaged_main(ret);
qemu_fclose(packf);
--
2.44.0
