[Qemu-devel] Re: [PATCH] migration: Issue 'cont' only on successful incoming migration

[Luiz Capitulino <lcapitulino@redhat.com>]

On Fri, 23 Jul 2010 16:15:15 +0530
Amit Shah <amit.shah@redhat.com> wrote:

> When a 'cont' is issued on a VM that's just waiting for an incoming
> migration, the VM reboots and boots into the guest, possibly corrupting
> its storage since it could be shared with another VM running elsewhere.
> 
> Ensure that a VM started with '-incoming' is only run when an incoming
> migration successfully completes.
> 
> Reported-by: Laine Stump <laine@redhat.com>
> Signed-off-by: Amit Shah <amit.shah@redhat.com>
> ---
>  migration.c |    3 +++
>  monitor.c   |    4 ++++
>  sysemu.h    |    1 +
>  vl.c        |    3 +++
>  4 files changed, 11 insertions(+), 0 deletions(-)
> 
> diff --git a/migration.c b/migration.c
> index 650eb78..84d7e4a 100644
> --- a/migration.c
> +++ b/migration.c
> @@ -67,6 +67,9 @@ void process_incoming_migration(QEMUFile *f)
>      qemu_announce_self();
>      DPRINTF("successfully loaded vm state\n");
>  
> +    incoming_expected = false;
> +    incoming_done = true;
> +
>      if (autostart)
>          vm_start();
>  }
> diff --git a/monitor.c b/monitor.c
> index 45fd482..d12a7b5 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -1056,6 +1056,10 @@ static int do_cont(Monitor *mon, const QDict *qdict, QObject **ret_data)
>  {
>      struct bdrv_iterate_context context = { mon, 0 };
>  
> +    if (incoming_expected && !incoming_done) {
> +        autostart = 1;

Why do we need to set autostart? We should just fail if we're unable to run.

> +        return 1; /* Waiting for incoming migration */

You should return -1 and use qerror_report(), so that we have a meaningful
error in the user Monitor and QMP (otherwise we'll get UndefinedError).

And incomding_done is not needed.

> +    }
>      bdrv_iterate(encrypted_bdrv_it, &context);
>      /* only resume the vm if all keys are set and valid */
>      if (!context.err) {
> diff --git a/sysemu.h b/sysemu.h
> index 9c988bb..f9c1962 100644
> --- a/sysemu.h
> +++ b/sysemu.h
> @@ -99,6 +99,7 @@ typedef enum DisplayType
>  } DisplayType;
>  
>  extern int autostart;
> +extern int incoming_expected, incoming_done;
>  extern int bios_size;
>  
>  typedef enum {
> diff --git a/vl.c b/vl.c
> index ba6ee11..b69c11b 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -182,6 +182,8 @@ int nb_nics;
>  NICInfo nd_table[MAX_NICS];
>  int vm_running;
>  int autostart;
> +int incoming_expected; /* Started with -incoming and waiting for incoming */
> +int incoming_done; /* Incoming migration successful */
>  static int rtc_utc = 1;
>  static int rtc_date_offset = -1; /* -1 means no change */
>  QEMUClock *rtc_clock;
> @@ -2557,6 +2559,7 @@ int main(int argc, char **argv, char **envp)
>                  break;
>              case QEMU_OPTION_incoming:
>                  incoming = optarg;
> +                incoming_expected = true;
>                  break;
>              case QEMU_OPTION_nodefaults:
>                  default_serial = 0;