[Qemu-devel] [PATCH] migration: isolate return path on src

[Qemu-devel] [PATCH] migration: isolate return path on src

[Peter Xu]

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 <peterx@redhat.com>
---
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);
+    }
 
+    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

Re: [Qemu-devel] [PATCH] migration: isolate return path on src

[Juan Quintela]

Peter Xu <peterx@redhat.com> 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 <peterx@redhat.com>
> ---
> 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.


Reviewed-by: Juan Quintela <quintela@redhat.com>

queued

Re: [Qemu-devel] [PATCH] migration: isolate return path on src

[Dr. David Alan Gilbert]

* Peter Xu (peterx@redhat.com) 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 <peterx@redhat.com>
> ---
> 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 / dgilbert@redhat.com / Manchester, UK

Re: [Qemu-devel] [PATCH] migration: isolate return path on src

[Juan Quintela]

"Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> * Peter Xu (peterx@redhat.com) 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 <peterx@redhat.com>
>> ---
>> 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.

You are right.

Second chunk makes no sense.  I told Peter to split the
"objectification" of migration state and this patch.  This made more
sense when the user *had* required a return path.

Good catch.

Thanks, Juan.

Re: [Qemu-devel] [PATCH] migration: isolate return path on src

[Peter Xu]

On Wed, May 31, 2017 at 08:33:01PM +0200, Juan Quintela wrote:
> "Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> > * Peter Xu (peterx@redhat.com) 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 <peterx@redhat.com>
> >> ---
> >> 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.
> 
> You are right.
> 
> Second chunk makes no sense.  I told Peter to split the
> "objectification" of migration state and this patch.  This made more
> sense when the user *had* required a return path.

Oops! I believe it should be what Dave mentioned
(s->rp_state.from_dst_file rather than s->to_dst_file). Sorry!

I'll repost to see whether we'd like the new one. Thanks,

-- 
Peter Xu