Re: [Xen-devel] [PATCH v8 2/6] Introduce "xen-save-devices-state"

[Luiz Capitulino <lcapitulino@xxxxxxxxxx>]

On Mon, 19 Mar 2012 11:48:01 +0000
Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx> wrote:

> - add an "is_ram" flag to SaveStateEntry;
> 
> - register_savevm_live sets is_ram for live_savevm devices;
> 
> - introduce a "xen-save-devices-state" QAPI command that can be used to save
> the state of all devices, but not the RAM or the block devices of the
> VM.
> 
> Changes in v8:
> 
> - rename save-devices-state to xen-save-devices-state.
> 
> Changes in v7:
> 
> - rename save_devices to save-devices-state.
> 
> Changes in v6:
> 
> - remove the is_ram parameter from register_savevm_live and sets is_ram
> if the device is a live_savevm device;
> 
> - introduce save_devices as a QAPI command, write a better description
> for it;
> 
> - fix CODING_STYLE;
> 
> - introduce a new doc to explain the save format used by save_devices.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> Reviewed-by: Anthony Liguori <aliguori@xxxxxxxxxx>

Acked-by: Luiz Capitulino <lcapitulino@xxxxxxxxxx>

> ---
>  docs/xen-save-devices-state.txt |   34 ++++++++++++++++++
>  qapi-schema.json                |   19 ++++++++++
>  qmp-commands.hx                 |   27 +++++++++++++++
>  savevm.c                        |   71 
> +++++++++++++++++++++++++++++++++++++++
>  4 files changed, 151 insertions(+), 0 deletions(-)
>  create mode 100644 docs/xen-save-devices-state.txt
> 
> diff --git a/docs/xen-save-devices-state.txt b/docs/xen-save-devices-state.txt
> new file mode 100644
> index 0000000..92e08db
> --- /dev/null
> +++ b/docs/xen-save-devices-state.txt
> @@ -0,0 +1,34 @@
> += Save Devices =
> +
> +QEMU has code to load/save the state of the guest that it is running.
> +These are two complementary operations.  Saving the state just does
> +that, saves the state for each device that the guest is running.
> +
> +These operations are normally used with migration (see migration.txt),
> +however it is also possible to save the state of all devices to file,
> +without saving the RAM or the block devices of the VM.
> +
> +This operation is called "xen-save-devices-state" (see
> +QMP/qmp-commands.txt)
> +
> +
> +The binary format used in the file is the following:
> +
> +
> +-------------------------------------------
> +
> +32 bit big endian: QEMU_VM_FILE_MAGIC
> +32 bit big endian: QEMU_VM_FILE_VERSION
> +
> +for_each_device
> +{
> +    8 bit:              QEMU_VM_SECTION_FULL
> +    32 bit big endian:  section_id
> +    8 bit:              idstr (ID string) length
> +    string:             idstr (ID string)
> +    32 bit big endian:  instance_id
> +    32 bit big endian:  version_id
> +    buffer:             device specific data
> +}
> +
> +8 bit: QEMU_VM_EOF
> diff --git a/qapi-schema.json b/qapi-schema.json
> index d0b6792..def69a9 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -1593,3 +1593,22 @@
>  { 'command': 'qom-list-types',
>    'data': { '*implements': 'str', '*abstract': 'bool' },
>    'returns': [ 'ObjectTypeInfo' ] }
> +
> +##
> +# @xen-save-devices-state:
> +#
> +# Save the state of all devices to file. The RAM and the block devices
> +# of the VM are not saved by this command.
> +#
> +# @filename: the file to save the state of the devices to as binary
> +# data. See xen-save-devices-state.txt for a description of the binary
> +# format.
> +#
> +# Returns: Nothing on success
> +#          If @filename cannot be opened, OpenFileFailed
> +#          If an I/O error occurs while writing the file, IOError
> +#
> +# Since: 1.1
> +##
> +{ 'command': 'xen-save-devices-state', 'data': {'filename': 'str'} }
> +
> diff --git a/qmp-commands.hx b/qmp-commands.hx
> index 705f704..dbb6236 100644
> --- a/qmp-commands.hx
> +++ b/qmp-commands.hx
> @@ -444,6 +444,33 @@ Note: inject-nmi is only supported for x86 guest 
> currently, it will
>  EQMP
>  
>      {
> +        .name       = "xen-save-devices-state",
> +        .args_type  = "filename:F",
> +    .mhandler.cmd_new = qmp_marshal_input_xen_save_devices_state,
> +    },
> +
> +SQMP
> +xen-save-devices-state
> +-------
> +
> +Save the state of all devices to file. The RAM and the block devices
> +of the VM are not saved by this command.
> +
> +Arguments:
> +
> +- "filename": the file to save the state of the devices to as binary
> +data. See xen-save-devices-state.txt for a description of the binary
> +format.
> +
> +Example:
> +
> +-> { "execute": "xen-save-devices-state",
> +     "arguments": { "filename": "/tmp/save" } }
> +<- { "return": {} }
> +
> +EQMP
> +
> +    {
>          .name       = "migrate",
>          .args_type  = "detach:-d,blk:-b,inc:-i,uri:s",
>          .params     = "[-d] [-b] [-i] uri",
> diff --git a/savevm.c b/savevm.c
> index 80be1ff..0e61eb0 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -84,6 +84,7 @@
>  #include "qemu-timer.h"
>  #include "cpus.h"
>  #include "memory.h"
> +#include "qmp-commands.h"
>  
>  #define SELF_ANNOUNCE_ROUNDS 5
>  
> @@ -1177,6 +1178,7 @@ typedef struct SaveStateEntry {
>      void *opaque;
>      CompatEntry *compat;
>      int no_migrate;
> +    int is_ram;
>  } SaveStateEntry;
>  
>  
> @@ -1241,6 +1243,10 @@ int register_savevm_live(DeviceState *dev,
>      se->opaque = opaque;
>      se->vmsd = NULL;
>      se->no_migrate = 0;
> +    /* if this is a live_savem then set is_ram */
> +    if (save_live_state != NULL) {
> +        se->is_ram = 1;
> +    }
>  
>      if (dev && dev->parent_bus && dev->parent_bus->info->get_dev_path) {
>          char *id = dev->parent_bus->info->get_dev_path(dev);
> @@ -1728,6 +1734,45 @@ out:
>      return ret;
>  }
>  
> +static int qemu_save_device_state(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;
> +        }
> +        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);
> +}
> +
>  static SaveStateEntry *find_se(const char *idstr, int instance_id)
>  {
>      SaveStateEntry *se;
> @@ -2109,6 +2154,32 @@ void do_savevm(Monitor *mon, const QDict *qdict)
>          vm_start();
>  }
>  
> +void qmp_xen_save_devices_state(const char *filename, Error **errp)
> +{
> +    QEMUFile *f;
> +    int saved_vm_running;
> +    int ret;
> +
> +    saved_vm_running = runstate_is_running();
> +    vm_stop(RUN_STATE_SAVE_VM);
> +
> +    f = qemu_fopen(filename, "wb");
> +    if (!f) {
> +        error_set(errp, QERR_OPEN_FILE_FAILED, filename);
> +        goto the_end;
> +    }
> +    ret = qemu_save_device_state(f);
> +    qemu_fclose(f);
> +    if (ret < 0) {
> +        error_set(errp, QERR_IO_ERROR);
> +    }
> +
> + the_end:
> +    if (saved_vm_running)
> +        vm_start();
> +    return;
> +}
> +
>  int load_vmstate(const char *name)
>  {
>      BlockDriverState *bs, *bs_vm_state;


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