Re: [PATCH v6 2/6] Introduce "save_devices"

[Luiz Capitulino <lcapitulino@redhat.com>]

On Thu, 15 Mar 2012 15:16:15 -0500
Anthony Liguori <anthony@codemonkey.ws> wrote:

> On 03/15/2012 01:19 PM, Stefano Stabellini wrote:
> > - add an "is_ram" flag to SaveStateEntry;
> >
> > - register_savevm_live sets is_ram for live_savevm devices;
> >
> > - introduce a "save_devices" 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 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@eu.citrix.com>
> > CC: Anthony Liguori<anthony@codemonkey.ws>
> > CC: Luiz Capitulino<lcapitulino@redhat.com>
> > ---
> >   docs/save_devices.txt |   33 ++++++++++++++++++++++
> >   qapi-schema.json      |   18 ++++++++++++
> >   qmp-commands.hx       |   25 +++++++++++++++++
> >   savevm.c              |   71 +++++++++++++++++++++++++++++++++++++++++++++++++
> >   4 files changed, 147 insertions(+), 0 deletions(-)
> >   create mode 100644 docs/save_devices.txt
> >
> > diff --git a/docs/save_devices.txt b/docs/save_devices.txt
> > new file mode 100644
> > index 0000000..79915d2
> > --- /dev/null
> > +++ b/docs/save_devices.txt
> > @@ -0,0 +1,33 @@
> > += 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 "save_devices" (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..7f938ff 100644
> > --- a/qapi-schema.json
> > +++ b/qapi-schema.json
> > @@ -1593,3 +1593,21 @@
> >   { 'command': 'qom-list-types',
> >     'data': { '*implements': 'str', '*abstract': 'bool' },
> >     'returns': [ 'ObjectTypeInfo' ] }
> > +
> > +##
> > +# @save_devices:
> > +#
> > +# 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 save_devices.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: 1.0
> 
> Since: 1.1.
> 
> Otherwise Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>

Looks fine to me FWIW, my only nitpick is that we use an hyphen instead of the
underline in qmp command names, but I'd call this save-devices-state.

Don't you want this in HMP too, btw?

> 
> Regards,
> 
> Anthony Liguori
> 
> 
> > +##
> > +{ 'command': 'save_devices', 'data': {'filename': 'str'} }
> > +
> > diff --git a/qmp-commands.hx b/qmp-commands.hx
> > index 705f704..064d2a4 100644
> > --- a/qmp-commands.hx
> > +++ b/qmp-commands.hx
> > @@ -444,6 +444,31 @@ Note: inject-nmi is only supported for x86 guest currently, it will
> >   EQMP
> >
> >       {
> > +        .name       = "save_devices",
> > +        .args_type  = "filename:F",
> > +    .mhandler.cmd_new = qmp_marshal_input_save_devices,
> > +    },
> > +
> > +SQMP
> > +save_devices
> > +-------
> > +
> > +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 save_devices.txt for a description of the binary format.
> > +
> > +Example:
> > +
> > +->  { "execute": "save_devices", "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..148356a 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_save_devices(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;
>