On Fri, Apr 05, 2024 at 11:40:56AM +0800, Wei Wang wrote:
> 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.
>
> 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>
The current version doesn't have any of my credits. :) Thanks, but I'll
just drop it to reflect reality, so we keep the credit to the right ones.
> 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..63f9991a8a 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
> + * hasn't been dispatched.
I'll squash below into it. If any of you disagree please shoot: valid
until this Sunday.
+ * 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.
Huge thanks to both!
> + */
> + 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);
> --
> 2.27.0
>
--
Peter Xu
