Re: [Qemu-devel] [RFC v2 21/33] migration: new cmd MIG_CMD_POSTCOPY_RESUME

[Peter Xu]

On Fri, Sep 22, 2017 at 12:08:06PM +0100, Dr. David Alan Gilbert wrote:
> * Peter Xu (pet...@redhat.com) wrote:
> > Introducing this new command to be sent when the source VM is ready to
> > resume the paused migration.  What the destination does here is
> > basically release the fault thread to continue service page faults.
> > 
> > Signed-off-by: Peter Xu 
> > ---
> >  migration/savevm.c | 33 +
> >  migration/savevm.h |  1 +
> >  migration/trace-events |  1 +
> >  3 files changed, 35 insertions(+)
> > 
> > diff --git a/migration/savevm.c b/migration/savevm.c
> > index 7f77a31..e914346 100644
> > --- a/migration/savevm.c
> > +++ b/migration/savevm.c
> > @@ -77,6 +77,7 @@ enum qemu_vm_cmd {
> >  MIG_CMD_POSTCOPY_RAM_DISCARD,  /* A list of pages to discard that
> >were previously sent during
> >precopy but are dirty. */
> > +MIG_CMD_POSTCOPY_RESUME,   /* resume postcopy on dest */
> >  MIG_CMD_PACKAGED,  /* Send a wrapped stream within this stream 
> > */
> >  MIG_CMD_RECV_BITMAP,   /* Request for recved bitmap on dst */
> >  MIG_CMD_MAX
> > @@ -95,6 +96,7 @@ static struct mig_cmd_args {
> >  [MIG_CMD_POSTCOPY_RUN] = { .len =  0, .name = "POSTCOPY_RUN" },
> >  [MIG_CMD_POSTCOPY_RAM_DISCARD] = {
> > .len = -1, .name = 
> > "POSTCOPY_RAM_DISCARD" },
> > +[MIG_CMD_POSTCOPY_RESUME]  = { .len =  0, .name = "POSTCOPY_RESUME" },
> >  [MIG_CMD_PACKAGED] = { .len =  4, .name = "PACKAGED" },
> >  [MIG_CMD_RECV_BITMAP]  = { .len = -1, .name = "RECV_BITMAP" },
> >  [MIG_CMD_MAX]  = { .len = -1, .name = "MAX" },
> > @@ -931,6 +933,12 @@ void qemu_savevm_send_postcopy_run(QEMUFile *f)
> >  qemu_savevm_command_send(f, MIG_CMD_POSTCOPY_RUN, 0, NULL);
> >  }
> >  
> > +void qemu_savevm_send_postcopy_resume(QEMUFile *f)
> > +{
> > +trace_savevm_send_postcopy_resume();
> > +qemu_savevm_command_send(f, MIG_CMD_POSTCOPY_RESUME, 0, NULL);
> > +}
> > +
> >  void qemu_savevm_send_recv_bitmap(QEMUFile *f, char *block_name)
> >  {
> >  size_t len;
> > @@ -1682,6 +1690,28 @@ static int 
> > loadvm_postcopy_handle_run(MigrationIncomingState *mis)
> >  return LOADVM_QUIT;
> >  }
> >  
> > +static int loadvm_postcopy_handle_resume(MigrationIncomingState *mis)
> > +{
> > +if (mis->state != MIGRATION_STATUS_POSTCOPY_RECOVER) {
> > +error_report("%s: illegal resume received", __func__);
> > +/* Don't fail the load, only for this. */
> > +return 0;
> > +}
> > +
> > +/*
> > + * This means source VM is ready to resume the postcopy migration.
> > + * It's time to switch state and release the fault thread to
> > + * continue service page faults.
> > + */
> > +migrate_set_state(>state, MIGRATION_STATUS_POSTCOPY_RECOVER,
> > +  MIGRATION_STATUS_POSTCOPY_ACTIVE);
> > +qemu_sem_post(>postcopy_pause_sem_fault);
> > +
> > +/* TODO: Tell source that "we are ready" */
> > +
> 
> You might want to add a trace in here; however,

Added.

> 
> 
> Reviewed-by: Dr. David Alan Gilbert 

Thanks!

-- 
Peter Xu

Re: [Qemu-devel] [RFC v2 21/33] migration: new cmd MIG_CMD_POSTCOPY_RESUME

[Dr. David Alan Gilbert]

* Peter Xu (pet...@redhat.com) wrote:
> Introducing this new command to be sent when the source VM is ready to
> resume the paused migration.  What the destination does here is
> basically release the fault thread to continue service page faults.
> 
> Signed-off-by: Peter Xu 
> ---
>  migration/savevm.c | 33 +
>  migration/savevm.h |  1 +
>  migration/trace-events |  1 +
>  3 files changed, 35 insertions(+)
> 
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 7f77a31..e914346 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -77,6 +77,7 @@ enum qemu_vm_cmd {
>  MIG_CMD_POSTCOPY_RAM_DISCARD,  /* A list of pages to discard that
>were previously sent during
>precopy but are dirty. */
> +MIG_CMD_POSTCOPY_RESUME,   /* resume postcopy on dest */
>  MIG_CMD_PACKAGED,  /* Send a wrapped stream within this stream */
>  MIG_CMD_RECV_BITMAP,   /* Request for recved bitmap on dst */
>  MIG_CMD_MAX
> @@ -95,6 +96,7 @@ static struct mig_cmd_args {
>  [MIG_CMD_POSTCOPY_RUN] = { .len =  0, .name = "POSTCOPY_RUN" },
>  [MIG_CMD_POSTCOPY_RAM_DISCARD] = {
> .len = -1, .name = "POSTCOPY_RAM_DISCARD" 
> },
> +[MIG_CMD_POSTCOPY_RESUME]  = { .len =  0, .name = "POSTCOPY_RESUME" },
>  [MIG_CMD_PACKAGED] = { .len =  4, .name = "PACKAGED" },
>  [MIG_CMD_RECV_BITMAP]  = { .len = -1, .name = "RECV_BITMAP" },
>  [MIG_CMD_MAX]  = { .len = -1, .name = "MAX" },
> @@ -931,6 +933,12 @@ void qemu_savevm_send_postcopy_run(QEMUFile *f)
>  qemu_savevm_command_send(f, MIG_CMD_POSTCOPY_RUN, 0, NULL);
>  }
>  
> +void qemu_savevm_send_postcopy_resume(QEMUFile *f)
> +{
> +trace_savevm_send_postcopy_resume();
> +qemu_savevm_command_send(f, MIG_CMD_POSTCOPY_RESUME, 0, NULL);
> +}
> +
>  void qemu_savevm_send_recv_bitmap(QEMUFile *f, char *block_name)
>  {
>  size_t len;
> @@ -1682,6 +1690,28 @@ static int 
> loadvm_postcopy_handle_run(MigrationIncomingState *mis)
>  return LOADVM_QUIT;
>  }
>  
> +static int loadvm_postcopy_handle_resume(MigrationIncomingState *mis)
> +{
> +if (mis->state != MIGRATION_STATUS_POSTCOPY_RECOVER) {
> +error_report("%s: illegal resume received", __func__);
> +/* Don't fail the load, only for this. */
> +return 0;
> +}
> +
> +/*
> + * This means source VM is ready to resume the postcopy migration.
> + * It's time to switch state and release the fault thread to
> + * continue service page faults.
> + */
> +migrate_set_state(>state, MIGRATION_STATUS_POSTCOPY_RECOVER,
> +  MIGRATION_STATUS_POSTCOPY_ACTIVE);
> +qemu_sem_post(>postcopy_pause_sem_fault);
> +
> +/* TODO: Tell source that "we are ready" */
> +

You might want to add a trace in here; however,


Reviewed-by: Dr. David Alan Gilbert 

> +return 0;
> +}
> +
>  /**
>   * Immediately following this command is a blob of data containing an 
> embedded
>   * chunk of migration stream; read it and load it.
> @@ -1847,6 +1877,9 @@ static int loadvm_process_command(QEMUFile *f)
>  case MIG_CMD_POSTCOPY_RAM_DISCARD:
>  return loadvm_postcopy_ram_handle_discard(mis, len);
>  
> +case MIG_CMD_POSTCOPY_RESUME:
> +return loadvm_postcopy_handle_resume(mis);
> +
>  case MIG_CMD_RECV_BITMAP:
>  return loadvm_handle_recv_bitmap(mis, len);
>  }
> diff --git a/migration/savevm.h b/migration/savevm.h
> index 8126b1c..a5f3879 100644
> --- a/migration/savevm.h
> +++ b/migration/savevm.h
> @@ -46,6 +46,7 @@ int qemu_savevm_send_packaged(QEMUFile *f, const uint8_t 
> *buf, size_t len);
>  void qemu_savevm_send_postcopy_advise(QEMUFile *f);
>  void qemu_savevm_send_postcopy_listen(QEMUFile *f);
>  void qemu_savevm_send_postcopy_run(QEMUFile *f);
> +void qemu_savevm_send_postcopy_resume(QEMUFile *f);
>  void qemu_savevm_send_recv_bitmap(QEMUFile *f, char *block_name);
>  
>  void qemu_savevm_send_postcopy_ram_discard(QEMUFile *f, const char *name,
> diff --git a/migration/trace-events b/migration/trace-events
> index 9960cd8..0a1c302 100644
> --- a/migration/trace-events
> +++ b/migration/trace-events
> @@ -35,6 +35,7 @@ savevm_send_open_return_path(void) ""
>  savevm_send_ping(uint32_t val) "0x%x"
>  savevm_send_postcopy_listen(void) ""
>  savevm_send_postcopy_run(void) ""
> +savevm_send_postcopy_resume(void) ""
>  savevm_send_recv_bitmap(char *name) "%s"
>  savevm_state_setup(void) ""
>  savevm_state_header(void) ""
> -- 
> 2.7.4
> 
> 
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK