Re: [Qemu-devel] [PATCH RESEND v5 2/6] Introduce "save_devices"

[Anthony Liguori <anthony@codemonkey.ws>]

On 02/28/2012 09:51 AM, Stefano Stabellini wrote:
> - add an "is_ram" flag to SaveStateEntry;
>
> - add an "is_ram" parameter to register_savevm_live;
>
> - introduce a "save_devices" monitor command that can be used to save
> the state of non-ram devices.
>
> Signed-off-by: Stefano Stabellini<stefano.stabellini@eu.citrix.com>
> ---
>   block-migration.c |    2 +-
>   hmp-commands.hx   |   14 ++++++++++
>   qmp-commands.hx   |   17 ++++++++++++
>   savevm.c          |   72 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
>   sysemu.h          |    1 +
>   vl.c              |    2 +-
>   vmstate.h         |    1 +
>   7 files changed, 106 insertions(+), 3 deletions(-)
>
> diff --git a/block-migration.c b/block-migration.c
> index 4467468..d283fd0 100644
> --- a/block-migration.c
> +++ b/block-migration.c
> @@ -722,6 +722,6 @@ void blk_mig_init(void)
>       QSIMPLEQ_INIT(&block_mig_state.bmds_list);
>       QSIMPLEQ_INIT(&block_mig_state.blk_list);
>
> -    register_savevm_live(NULL, "block", 0, 1, block_set_params,
> +    register_savevm_live(NULL, "block", 0, 1, 0, block_set_params,
>                            block_save_live, NULL, block_load,&block_mig_state);

Do you really want the block live migration to be part of Xen?

If not, then you can simplify by just making register_savevm_live always imply 
!device and adjust register_savevm() accordingly.  Otherwise, the likelihood of 
a casual observer knowing what '0, 1, 0' means is pretty bad...

>   }
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index 64b3656..873abc9 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -280,6 +280,20 @@ a snapshot with the same tag or ID, it is replaced. More info at
>   ETEXI
>
>       {
> +        .name       = "save_devices",
> +        .args_type  = "filename:F",
> +        .params     = "filename",
> +        .help       = "save the state of non-ram devices.",
> +        .mhandler.cmd_new = do_save_device_state,
> +    },
> +
> +STEXI
> +@item save_devices @var{filename}
> +@findex save_devices
> +Save the state of non-ram devices.
> +ETEXI
> +
> +    {
>           .name       = "loadvm",
>           .args_type  = "name:s",
>           .params     = "tag|id",
> diff --git a/qmp-commands.hx b/qmp-commands.hx
> index 705f704..619d9de 100644
> --- a/qmp-commands.hx
> +++ b/qmp-commands.hx
> @@ -444,6 +444,23 @@ Note: inject-nmi is only supported for x86 guest currently, it will
>   EQMP
>
>       {
> +        .name       = "save_devices",
> +        .args_type  = "filename:F",
> +        .params     = "filename",
> +        .help       = "save the state of non-ram devices.",
> +        .user_print = monitor_user_noop,	
> +    .mhandler.cmd_new = do_save_device_state,
> +    },
> +
> +SQMP
> +save_devices
> +-------
> +
> +Save the state of non-ram devices.
> +
> +EQMP
> +
> +    {
>           .name       = "migrate",
>           .args_type  = "detach:-d,blk:-b,inc:-i,uri:s",
>           .params     = "[-d] [-b] [-i] uri",


Should be QAPI commands and documented a great deal more (see other examples in 
qapi-schema.json).  Please CC Luiz too when adding new QMP commands.

> diff --git a/savevm.c b/savevm.c
> index 80be1ff..d0e62bb 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -1177,6 +1177,7 @@ typedef struct SaveStateEntry {
>       void *opaque;
>       CompatEntry *compat;
>       int no_migrate;
> +    int is_ram;
>   } SaveStateEntry;
>
>
> @@ -1223,6 +1224,7 @@ int register_savevm_live(DeviceState *dev,
>                            const char *idstr,
>                            int instance_id,
>                            int version_id,
> +                         int is_ram,
>                            SaveSetParamsHandler *set_params,
>                            SaveLiveStateHandler *save_live_state,
>                            SaveStateHandler *save_state,
> @@ -1241,6 +1243,7 @@ int register_savevm_live(DeviceState *dev,
>       se->opaque = opaque;
>       se->vmsd = NULL;
>       se->no_migrate = 0;
> +    se->is_ram = is_ram;
>
>       if (dev&&  dev->parent_bus&&  dev->parent_bus->info->get_dev_path) {
>           char *id = dev->parent_bus->info->get_dev_path(dev);
> @@ -1277,7 +1280,7 @@ int register_savevm(DeviceState *dev,
>                       LoadStateHandler *load_state,
>                       void *opaque)
>   {
> -    return register_savevm_live(dev, idstr, instance_id, version_id,
> +    return register_savevm_live(dev, idstr, instance_id, version_id, 0,
>                                   NULL, NULL, save_state, load_state, opaque);
>   }
>
> @@ -1728,6 +1731,43 @@ out:
>       return ret;
>   }
>
> +static int qemu_save_device_state(Monitor *mon, QEMUFile *f)
> +{
> +    SaveStateEntry *se;
> +
> +    qemu_put_be32(f, QEMU_VM_FILE_MAGIC);
> +    qemu_put_be32(f, QEMU_VM_FILE_VERSION);
> +
> +    cpu_synchronize_all_states();
> +
> +    QTAILQ_FOREACH(se,&savevm_handlers, entry) {
> +        int len;
> +
> +        if (se->is_ram)
> +            continue;

Violating CODING_STYLE.

> +        if (se->save_state == NULL&&  se->vmsd == NULL)
> +            continue;
> +
> +        /* Section type */
> +        qemu_put_byte(f, QEMU_VM_SECTION_FULL);
> +        qemu_put_be32(f, se->section_id);
> +
> +        /* ID string */
> +        len = strlen(se->idstr);
> +        qemu_put_byte(f, len);
> +        qemu_put_buffer(f, (uint8_t *)se->idstr, len);
> +
> +        qemu_put_be32(f, se->instance_id);
> +        qemu_put_be32(f, se->version_id);
> +
> +        vmstate_save(f, se);
> +    }
> +
> +    qemu_put_byte(f, QEMU_VM_EOF);
> +
> +    return qemu_file_get_error(f);
> +}

Please add something to docs/ documenting this format.

> +
>   static SaveStateEntry *find_se(const char *idstr, int instance_id)
>   {
>       SaveStateEntry *se;
> @@ -2109,6 +2149,36 @@ void do_savevm(Monitor *mon, const QDict *qdict)
>           vm_start();
>   }
>
> +int do_save_device_state(Monitor *mon, const QDict *qdict, QObject **ret_data)
> +{
> +    int ret;
> +    QEMUFile *f;
> +    int saved_vm_running;
> +    const char *filename = qdict_get_try_str(qdict, "filename");
> +
> +    saved_vm_running = runstate_is_running();
> +    vm_stop(RUN_STATE_SAVE_VM);
> +
> +    f = qemu_fopen(filename, "wb");
> +    if (!f) {
> +        monitor_printf(mon, "Could not open VM state file\n");
> +        ret = -1;
> +        goto the_end;
> +    }
> +    ret = qemu_save_device_state(mon, f);
> +    qemu_fclose(f);
> +    if (ret<  0) {
> +        monitor_printf(mon, "Error %d while writing VM\n", ret);
> +        goto the_end;
> +    }
> +    ret = 0;
> +
> + the_end:
> +    if (saved_vm_running)
> +        vm_start();
> +    return ret;
> +}
> +

Would it be useful/interesting to return a binary blob via QMP instead of 
writing to a file?

Regards,

Anthony Liguori

>   int load_vmstate(const char *name)
>   {
>       BlockDriverState *bs, *bs_vm_state;
> diff --git a/sysemu.h b/sysemu.h
> index 98118cc..f4d5bf4 100644
> --- a/sysemu.h
> +++ b/sysemu.h
> @@ -70,6 +70,7 @@ void qemu_remove_exit_notifier(Notifier *notify);
>   void qemu_add_machine_init_done_notifier(Notifier *notify);
>
>   void do_savevm(Monitor *mon, const QDict *qdict);
> +int do_save_device_state(Monitor *mon, const QDict *qdict, QObject **ret_data);
>   int load_vmstate(const char *name);
>   void do_delvm(Monitor *mon, const QDict *qdict);
>   void do_info_snapshots(Monitor *mon);
> diff --git a/vl.c b/vl.c
> index 1d4c350..5b2b84c 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -3393,7 +3393,7 @@ int main(int argc, char **argv, char **envp)
>       default_drive(default_sdcard, snapshot, machine->use_scsi,
>                     IF_SD, 0, SD_OPTS);
>
> -    register_savevm_live(NULL, "ram", 0, 4, NULL, ram_save_live, NULL,
> +    register_savevm_live(NULL, "ram", 0, 4, 1, NULL, ram_save_live, NULL,
>                            ram_load, NULL);
>
>       if (nb_numa_nodes>  0) {
> diff --git a/vmstate.h b/vmstate.h
> index 9d3c49c..3cef117 100644
> --- a/vmstate.h
> +++ b/vmstate.h
> @@ -44,6 +44,7 @@ int register_savevm_live(DeviceState *dev,
>                            const char *idstr,
>                            int instance_id,
>                            int version_id,
> +                         int is_ram,
>                            SaveSetParamsHandler *set_params,
>                            SaveLiveStateHandler *save_live_state,
>                            SaveStateHandler *save_state,