Re: [PATCH v5 42/50] multi-process/mig: Send VMSD of remote to the Proxy object

[Elena Ufimtseva]

On Thu, Mar 05, 2020 at 02:39:49PM +0000, Dr. David Alan Gilbert wrote:
> * Jagannathan Raman (address@hidden) wrote:
> > The remote process sends the VMSD to the Proxy object, on the source
> > side
> > 
> > Signed-off-by: Elena Ufimtseva <address@hidden>
> > Signed-off-by: John G Johnson <address@hidden>
> > Signed-off-by: Jagannathan Raman <address@hidden>
> > ---
> >  migration/savevm.c   | 27 +++++++++++++++++++++++++++
> >  migration/savevm.h   |  2 ++
> >  remote/remote-main.c | 43 +++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 72 insertions(+)
> > 
> > diff --git a/migration/savevm.c b/migration/savevm.c
> > index 1d4220e..09af14d 100644
> > --- a/migration/savevm.c
> > +++ b/migration/savevm.c
> > @@ -2942,3 +2942,30 @@ bool vmstate_check_only_migratable(const 
> > VMStateDescription *vmsd)
> >  
> >      return !(vmsd && vmsd->unmigratable);
> >  }
> > +
> 
> Can we add something here commenting, e.g.
> /* Called by the remote process to serialise migration back to the qemu
>  * */

Will add this.
> > +int qemu_remote_savevm(QEMUFile *f)
> > +{
> > +    SaveStateEntry *se;
> > +    int ret;
> > +
> > +    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
> > +        if (!se->vmsd || !vmstate_save_needed(se->vmsd, se->opaque)) {
> > +            continue;
> > +        }
> > +
> > +        save_section_header(f, se, QEMU_VM_SECTION_FULL);
> > +
> > +        ret = vmstate_save(f, se, NULL);
> > +        if (ret) {
> > +            qemu_file_set_error(f, ret);
> > +            return ret;
> > +        }
> > +
> > +        save_section_footer(f, se);
> > +    }
> > +
> > +    qemu_put_byte(f, QEMU_VM_EOF);
> > +    qemu_fflush(f);
> 
> You have a qemu_fflush in process_start_mig_out  just after you call it
> - so you don't need both; I suggest you remove this one.
>
Ok. 
> > +    return 0;
> 
> And make this return qemu_file_get_error(f);  just like
> qemu_save_device_state and then makybe some day we can merge them.
>
Will do.
> > +}
> 
> 
> > diff --git a/migration/savevm.h b/migration/savevm.h
> > index ba64a7e..0491d3a 100644
> > --- a/migration/savevm.h
> > +++ b/migration/savevm.h
> > @@ -65,4 +65,6 @@ void qemu_loadvm_state_cleanup(void);
> >  int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis);
> >  int qemu_load_device_state(QEMUFile *f);
> >  
> > +int qemu_remote_savevm(QEMUFile *f);
> > +
> >  #endif
> > diff --git a/remote/remote-main.c b/remote/remote-main.c
> > index 58d9905..e97eb76 100644
> > --- a/remote/remote-main.c
> > +++ b/remote/remote-main.c
> > @@ -53,6 +53,16 @@
> >  #include "qemu/log.h"
> >  #include "qemu/cutils.h"
> >  #include "remote-opts.h"
> > +#include "qapi/error.h"
> > +#include "io/channel-util.h"
> > +
> > +#include "io/channel.h"
> > +#include "io/channel-socket.h"
> > +#include "migration/qemu-file-types.h"
> > +#include "migration/savevm.h"
> > +#include "migration/qemu-file-channel.h"
> > +#include "migration/qemu-file.h"
> > +
> >  #include "monitor/monitor.h"
> >  #include "chardev/char.h"
> >  #include "sysemu/reset.h"
> > @@ -322,6 +332,36 @@ static int setup_device(MPQemuMsg *msg, Error **errp)
> >  
> >  }
> >  
> > +static void process_start_mig_out(MPQemuMsg *msg)
> > +{
> > +    int wait = msg->fds[1];
> > +    Error *err = NULL;
> > +    QIOChannel *ioc;
> > +    QEMUFile *f;
> > +
> > +    ioc = qio_channel_new_fd(msg->fds[0], &err);
> > +    if (err) {
> > +        error_report_err(err);
> > +        return;
> > +    }
> > +
> > +    qio_channel_set_name(QIO_CHANNEL(ioc), "remote-migration-channel");
> > +
> > +    f = qemu_fopen_channel_output(ioc);
> > +
> > +    bdrv_drain_all();
> > +    (void)bdrv_flush_all();
> 
> Do remote process always have block code? I mean can't we have a remote
> process that's just say a NIC ?

Not always (in the future), we will account for this.

> 
> > +    (void)qemu_remote_savevm(f);
> 
> It's probably bad to ignore errors here; what you could do is if there's
> an error, you shoul dprint something and then send a poison value back
> to the QEMU to let it know that you've failed.
> 

Yes, will add this.

> > +    qemu_fflush(f);
> > +
> > +    notify_proxy(wait, (uint64_t)qemu_ftell(f));
> > +    PUT_REMOTE_WAIT(wait);
> > +
> > +    qemu_fclose(f);
> > +}
> > +
> >  static void process_msg(GIOCondition cond, MPQemuChannel *chan)
> >  {
> >      MPQemuMsg *msg = NULL;
> > @@ -411,6 +451,9 @@ static void process_msg(GIOCondition cond, 
> > MPQemuChannel *chan)
> >              notify_proxy(msg->fds[0], 0);
> >          }
> >          break;
> > +    case START_MIG_OUT:
> > +        process_start_mig_out(msg);
> > +        break;
> >      default:
> >          error_setg(&err, "Unknown command");
> >          goto finalize_loop;
> > -- 
> > 1.8.3.1
> 
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK
>