Re: [Qemu-devel] [PATCH 7/9] global_state: Make section optional

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Juan Quintela (quintela@redhat.com) wrote:
> This section would be sent:
> 
> a- for all new machine types
> b- for old achine types if section state is different form {running,paused}
>    that were the only giving us troubles.
> 
> So, in new qemus: it is alwasy there.  In old qemus: they are only
> there if it an error has happened, basically stoping on target.

I worry about whether we should do that for old machine types;
in the current code, if the destination was started with -S  it wouldn't
start in the case you were worried about, couldn't a careful managment
layer spot-the state on the source and ensure it didn't start the destination?

(What happens with guests that have been shutdown during a migrate, or panic
or something - not that I'm sure what happens now).

> Signed-off-by: Juan Quintela <quintela@redhat.com>
> ---
>  hw/i386/pc_piix.c             |  2 ++
>  hw/i386/pc_q35.c              |  2 ++
>  include/migration/migration.h |  2 +-
>  migration/migration.c         | 29 +++++++++++++++++++++++++++++
>  4 files changed, 34 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> index 212e263..5c04784 100644
> --- a/hw/i386/pc_piix.c
> +++ b/hw/i386/pc_piix.c
> @@ -52,6 +52,7 @@
>  #ifdef CONFIG_XEN
>  #  include <xen/hvm/hvm_info_table.h>
>  #endif
> +#include "migration/migration.h"
> 
>  #define MAX_IDE_BUS 2
> 
> @@ -312,6 +313,7 @@ static void pc_init_pci(MachineState *machine)
> 
>  static void pc_compat_2_3(MachineState *machine)
>  {
> +    global_state_set_optional();
>  }
> 
>  static void pc_compat_2_2(MachineState *machine)
> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> index e67f2de..cc5827a 100644
> --- a/hw/i386/pc_q35.c
> +++ b/hw/i386/pc_q35.c
> @@ -45,6 +45,7 @@
>  #include "hw/usb.h"
>  #include "hw/cpu/icc_bus.h"
>  #include "qemu/error-report.h"
> +#include "migration/migration.h"
> 
>  /* ICH9 AHCI has 6 ports */
>  #define MAX_SATA_PORTS     6
> @@ -291,6 +292,7 @@ static void pc_q35_init(MachineState *machine)
> 
>  static void pc_compat_2_3(MachineState *machine)
>  {
> +    global_state_set_optional();
>  }
> 
>  static void pc_compat_2_2(MachineState *machine)
> diff --git a/include/migration/migration.h b/include/migration/migration.h
> index 785c2dc..f939d88 100644
> --- a/include/migration/migration.h
> +++ b/include/migration/migration.h
> @@ -183,5 +183,5 @@ size_t ram_control_save_page(QEMUFile *f, ram_addr_t block_offset,
>  void register_global_state(void);
>  void global_state_store(void);
>  char *global_state_get_runstate(void);
> -
> +void global_state_set_optional(void);
>  #endif
> diff --git a/migration/migration.c b/migration/migration.c
> index ab69f81..1035689 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -868,6 +868,7 @@ void migrate_fd_connect(MigrationState *s)
>  }
> 
>  typedef struct {
> +    bool optional;
>      int32_t size;
>      uint8_t runstate[100];
>  } GlobalState;
> @@ -888,6 +889,33 @@ char *global_state_get_runstate(void)
>      return (char *)global_state.runstate;
>  }
> 
> +void global_state_set_optional(void)
> +{
> +    global_state.optional = true;
> +}


It's a shame that it's not really a device class, because then
you could have used a DEFINE_PROP_BIT.

> +static bool global_state_needed(void *opaque)
> +{
> +    GlobalState *s = opaque;
> +    char *runstate = (char *)s->runstate;
> +
> +    /* If it is not optional, it is mandatory */
> +
> +    if (s->optional == false) {
> +        return true;
> +    }
> +
> +    /* If state is running or paused, it is not needed */
> +
> +    if (strcmp(runstate, "running") == 0 ||
> +        strcmp(runstate, "paused") == 0) {
> +        return false;
> +    }
> +
> +    /* for any other state it is needed */
> +    return true;
> +}
> +
>  static int global_state_post_load(void *opaque, int version_id)
>  {
>      GlobalState *s = opaque;
> @@ -921,6 +949,7 @@ static const VMStateDescription vmstate_globalstate = {
>      .minimum_version_id = 1,
>      .post_load = global_state_post_load,
>      .pre_save = global_state_pre_save,
> +    .needed = global_state_needed,
>      .fields = (VMStateField[]) {
>          VMSTATE_INT32(size, GlobalState),
>          VMSTATE_BUFFER(runstate, GlobalState),
> -- 
> 2.4.0
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK