Re: [Qemu-devel] [PATCH v4 1/1] Introduce "xen-load-devices-state"

[Amit Shah]

Dave, can you take a look?

Thanks,

On (Mon) 11 Apr 2016 [11:56:02], Changlong Xie wrote:
> From: Wen Congyang <address@hidden>
> 
> Introduce a "xen-load-devices-state" QAPI command that can be used to
> load the state of all devices, but not the RAM or the block devices of
> the VM.
> 
> We only have hmp commands savevm/loadvm, and qmp commands
> xen-save-devices-state.
> 
> We use this new command for COLO:
> 1. suspend both primary vm and secondary vm
> 2. sync the state
> 3. resume both primary vm and secondary vm
> 
> In such case, we need to update all devices' state in any time.
> 
> Signed-off-by: Wen Congyang <address@hidden>
> Signed-off-by: Changlong Xie <address@hidden>
> ---
>  migration/savevm.c | 36 ++++++++++++++++++++++++++++++++++++
>  qapi-schema.json   | 14 ++++++++++++++
>  qmp-commands.hx    | 27 +++++++++++++++++++++++++++
>  3 files changed, 77 insertions(+)
> 
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 16ba443..d361a29 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -30,6 +30,7 @@
>  #include "hw/boards.h"
>  #include "hw/hw.h"
>  #include "hw/qdev.h"
> +#include "hw/xen/xen.h"
>  #include "net/net.h"
>  #include "monitor/monitor.h"
>  #include "sysemu/sysemu.h"
> @@ -1775,6 +1776,12 @@ qemu_loadvm_section_start_full(QEMUFile *f, 
> MigrationIncomingState *mis)
>          return -EINVAL;
>      }
>  
> +    /* Validate if it is a device's state */
> +    if (xen_enabled() && se->is_ram) {
> +        error_report("loadvm: %s RAM loading not allowed on Xen", idstr);
> +        return -EINVAL;
> +    }
> +
>      /* Add entry */
>      le = g_malloc0(sizeof(*le));
>  
> @@ -2084,6 +2091,35 @@ void qmp_xen_save_devices_state(const char *filename, 
> Error **errp)
>      }
>  }
>  
> +void qmp_xen_load_devices_state(const char *filename, Error **errp)
> +{
> +    QEMUFile *f;
> +    int ret;
> +
> +    /* Guest must be paused before loading the device state; the RAM state
> +     * will already have been loaded by xc
> +     */
> +    if (runstate_is_running()) {
> +        error_setg(errp, "Cannot update device state while vm is running");
> +        return;
> +    }
> +    vm_stop(RUN_STATE_RESTORE_VM);
> +
> +    f = qemu_fopen(filename, "rb");
> +    if (!f) {
> +        error_setg_file_open(errp, errno, filename);
> +        return;
> +    }
> +
> +    migration_incoming_state_new(f);
> +    ret = qemu_loadvm_state(f);
> +    qemu_fclose(f);
> +    if (ret < 0) {
> +        error_setg(errp, QERR_IO_ERROR);
> +    }
> +    migration_incoming_state_destroy();
> +}
> +
>  int load_vmstate(const char *name)
>  {
>      BlockDriverState *bs, *bs_vm_state;
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 54634c4..132264f 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -4144,6 +4144,20 @@
>    'data': [ 'none', 'record', 'play' ] }
>  
>  ##
> +# @xen-load-devices-state:
> +#
> +# Load the state of all devices from file. The RAM and the block devices
> +# of the VM are not loaded by this command.
> +#
> +# @filename: the file to load the state of the devices from as binary
> +# data. See xen-save-devices-state.txt for a description of the binary
> +# format.
> +#
> +# Since: 2.7
> +##
> +{ 'command': 'xen-load-devices-state', 'data': {'filename': 'str'} }
> +
> +##
>  # @GICCapability:
>  #
>  # The struct describes capability for a specific GIC (Generic
> diff --git a/qmp-commands.hx b/qmp-commands.hx
> index de896a5..68620f6 100644
> --- a/qmp-commands.hx
> +++ b/qmp-commands.hx
> @@ -587,6 +587,33 @@ Example:
>  EQMP
>  
>      {
> +        .name       = "xen-load-devices-state",
> +        .args_type  = "filename:F",
> +        .mhandler.cmd_new = qmp_marshal_xen_load_devices_state,
> +    },
> +
> +SQMP
> +xen-load-devices-state
> +----------------------
> +
> +Load the state of all devices from file. The RAM and the block devices
> +of the VM are not loaded by this command.
> +
> +Arguments:
> +
> +- "filename": the file to load the state of the devices from as binary
> +data. See xen-save-devices-state.txt for a description of the binary
> +format.
> +
> +Example:
> +
> +-> { "execute": "xen-load-devices-state",
> +     "arguments": { "filename": "/tmp/resume" } }
> +<- { "return": {} }
> +
> +EQMP
> +
> +    {
>          .name       = "xen-set-global-dirty-log",
>          .args_type  = "enable:b",
>          .mhandler.cmd_new = qmp_marshal_xen_set_global_dirty_log,
> -- 
> 1.9.3
> 
> 
> 

                Amit