Re: [Qemu-devel] [PATCH v3 2/2] migration: allow machine to enforce configuration section migration

[Laurent Vivier <lvivier@redhat.com>]

On 18/02/2016 12:32, Greg Kurz wrote:
> Migration of pseries-2.3 doesn't have configuration section. Unfortunately,
> QEMU 2.4/2.4.1/2.5 are buggy and always stream and expect the configuration
> section, and break migration both ways.
> 
> This patch introduces a property which allows to enforce a configuration
> section for machines who don't have one.
> 
> It can be set at startup:
> 
> -machine enforce-config-section=on
> 
> or later from the QEMU monitor:
> 
> qom-set /machine enforce-config-section on
> 
> It is up to the tooling to set or unset this property according to the
> version of the QEMU at the other end of the pipe.
> 
> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>

Reviewed-by: Laurent Vivier <lvivier@redhat.com>

> ---
>  hw/core/machine.c   |   21 +++++++++++++++++++++
>  include/hw/boards.h |    1 +
>  migration/savevm.c  |   10 ++++++++--
>  qemu-options.hx     |    3 ++-
>  4 files changed, 32 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index 6d1a0d8eebc4..a8c4680b0c47 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -312,6 +312,21 @@ static bool machine_get_suppress_vmdesc(Object *obj, Error **errp)
>      return ms->suppress_vmdesc;
>  }
>  
> +static void machine_set_enforce_config_section(Object *obj, bool value,
> +                                             Error **errp)
> +{
> +    MachineState *ms = MACHINE(obj);
> +
> +    ms->enforce_config_section = value;
> +}
> +
> +static bool machine_get_enforce_config_section(Object *obj, Error **errp)
> +{
> +    MachineState *ms = MACHINE(obj);
> +
> +    return ms->enforce_config_section;
> +}
> +
>  static int error_on_sysbus_device(SysBusDevice *sbdev, void *opaque)
>  {
>      error_report("Option '-device %s' cannot be handled by this machine",
> @@ -467,6 +482,12 @@ static void machine_initfn(Object *obj)
>      object_property_set_description(obj, "suppress-vmdesc",
>                                      "Set on to disable self-describing migration",
>                                      NULL);
> +    object_property_add_bool(obj, "enforce-config-section",
> +                             machine_get_enforce_config_section,
> +                             machine_set_enforce_config_section, NULL);
> +    object_property_set_description(obj, "enforce-config-section",
> +                                    "Set on to enforce configuration section migration",
> +                                    NULL);
>  
>      /* Register notifier when init is done for sysbus sanity checks */
>      ms->sysbus_notifier.notify = machine_init_notify;
> diff --git a/include/hw/boards.h b/include/hw/boards.h
> index 0f30959e2e3b..cfdf8d10cfcd 100644
> --- a/include/hw/boards.h
> +++ b/include/hw/boards.h
> @@ -128,6 +128,7 @@ struct MachineState {
>      char *firmware;
>      bool iommu;
>      bool suppress_vmdesc;
> +    bool enforce_config_section;
>  
>      ram_addr_t ram_size;
>      ram_addr_t maxram_size;
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 94f2894243ce..2fc57363674f 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -878,13 +878,19 @@ bool qemu_savevm_state_blocked(Error **errp)
>      return false;
>  }
>  
> +static bool enforce_config_section(void)
> +{
> +    MachineState *machine = MACHINE(qdev_get_machine());
> +    return machine->enforce_config_section;
> +}
> +
>  void qemu_savevm_state_header(QEMUFile *f)
>  {
>      trace_savevm_state_header();
>      qemu_put_be32(f, QEMU_VM_FILE_MAGIC);
>      qemu_put_be32(f, QEMU_VM_FILE_VERSION);
>  
> -    if (!savevm_state.skip_configuration) {
> +    if (!savevm_state.skip_configuration || enforce_config_section()) {
>          qemu_put_byte(f, QEMU_VM_CONFIGURATION);
>          vmstate_save_state(f, &vmstate_configuration, &savevm_state, 0);
>      }
> @@ -1875,7 +1881,7 @@ int qemu_loadvm_state(QEMUFile *f)
>          return -ENOTSUP;
>      }
>  
> -    if (!savevm_state.skip_configuration) {
> +    if (!savevm_state.skip_configuration || enforce_config_section()) {
>          if (qemu_get_byte(f) != QEMU_VM_CONFIGURATION) {
>              error_report("Configuration section missing");
>              return -EINVAL;
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 2f0465eeb1d1..8d81e310f2bf 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -43,7 +43,8 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
>      "                aes-key-wrap=on|off controls support for AES key wrapping (default=on)\n"
>      "                dea-key-wrap=on|off controls support for DEA key wrapping (default=on)\n"
>      "                suppress-vmdesc=on|off disables self-describing migration (default=off)\n"
> -    "                nvdimm=on|off controls NVDIMM support (default=off)\n",
> +    "                nvdimm=on|off controls NVDIMM support (default=off)\n"
> +    "                enforce-config-section=on|off enforce configuration section migration (default=off)\n",
>      QEMU_ARCH_ALL)
>  STEXI
>  @item -machine [type=]@var{name}[,prop=@var{value}[,...]]
>