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Re: [Qemu-devel] [PATCH] migration: isolate return path on src
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH] migration: isolate return path on src |
Date: |
Wed, 31 May 2017 18:05:38 +0100 |
User-agent: |
Mutt/1.8.2 (2017-04-18) |
* Peter Xu (address@hidden) wrote:
> There are some places that binded "return path" with postcopy. Let's be
> prepared for its usage even without postcopy. This patch mainly did this
> on source side.
>
> Signed-off-by: Peter Xu <address@hidden>
> ---
> standalone patch isolated from the return path series. ok to be picked
> up in case one day we'll re-face the return path enablement.
> With it, we are ready on source side. The dst side change has been queued.
> ---
> migration/migration.c | 11 ++++++-----
> migration/trace-events | 4 ++--
> 2 files changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/migration/migration.c b/migration/migration.c
> index ad29e53..96e549e 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1850,13 +1850,12 @@ static void migration_completion(MigrationState *s,
> int current_active_state,
> * cleaning everything else up (since if there are no failures
> * it will wait for the destination to send it's status in
> * a SHUT command).
> - * Postcopy opens rp if enabled (even if it's not avtivated)
> */
> - if (migrate_postcopy_ram()) {
> + if (s->rp_state.from_dst_file) {
> int rp_error;
> - trace_migration_completion_postcopy_end_before_rp();
> + trace_migration_return_path_end_before();
> rp_error = await_return_path_close_on_source(s);
> - trace_migration_completion_postcopy_end_after_rp(rp_error);
> + trace_migration_return_path_end_after(rp_error);
> if (rp_error) {
> goto fail_invalidate;
> }
> @@ -1931,13 +1930,15 @@ static void *migration_thread(void *opaque)
>
> qemu_savevm_state_header(s->to_dst_file);
>
> - if (migrate_postcopy_ram()) {
> + if (s->to_dst_file) {
> /* Now tell the dest that it should open its end so it can reply */
> qemu_savevm_send_open_return_path(s->to_dst_file);
>
> /* And do a ping that will make stuff easier to debug */
> qemu_savevm_send_ping(s->to_dst_file, 1);
I'm confused.
The migration_thread on the source will always have a s->to_dst_file
there so why test?
But also, we can't send the 'open return path' and 'send ping' messages
without a guard; sending them to old QEMUs will cause them to fail when
they don't know what the message is. I suspect sending them to
slightly-old QEMUs will cause them to fail when they try and send a
return message if the destination can't send it.
I can see a if (s->rp_state.from_dst_file) making some sense if it's
done at the right point.
Dave
> + }
>
> + if (migrate_postcopy_ram()) {
> /*
> * Tell the destination that we *might* want to do postcopy later;
> * if the other end can't do postcopy it should fail now, nice and
> diff --git a/migration/trace-events b/migration/trace-events
> index 5b8ccf3..38345be 100644
> --- a/migration/trace-events
> +++ b/migration/trace-events
> @@ -88,8 +88,8 @@ migrate_send_rp_message(int msg_type, uint16_t len) "%d:
> len %d"
> migration_completion_file_err(void) ""
> migration_completion_postcopy_end(void) ""
> migration_completion_postcopy_end_after_complete(void) ""
> -migration_completion_postcopy_end_before_rp(void) ""
> -migration_completion_postcopy_end_after_rp(int rp_error) "%d"
> +migration_return_path_end_before(void) ""
> +migration_return_path_end_after(int rp_error) "%d"
> migration_thread_after_loop(void) ""
> migration_thread_file_err(void) ""
> migration_thread_setup_complete(void) ""
> --
> 2.7.4
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK