Re: [Xen-devel] [Qemu-devel] [PATCH 19/18] Introduce "xen-load-devices-state"

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 24 Oct 2014, Wen Congyang wrote:
> 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 primay 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's state in any time.
> 
> Signed-off-by: Wen Congyang <wency@xxxxxxxxxxxxxx>
> Cc: qemu-devl <qemu-devel@xxxxxxxxxx>
> Cc: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>

The patch looks OK to me, far better than the previous version, but I am
no QMP expert.


>  qapi-schema.json | 18 ++++++++++++++++++
>  qmp-commands.hx  | 27 +++++++++++++++++++++++++++
>  savevm.c         | 36 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 81 insertions(+)
> 
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 391356f..c569856 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -4689,3 +4689,21 @@
>                'btn'     : 'InputBtnEvent',
>                'rel'     : 'InputMoveEvent',
>                'abs'     : 'InputMoveEvent' } }
> +
> +##
> +# @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.
> +#
> +# Returns: Nothing on success
> +#          If @filename cannot be opened, OpenFileFailed
> +#          If an I/O error occurs while reading the file, IOError
> +#
> +# Since: 2.0
> +##
> +{ 'command': 'xen-load-devices-state', 'data': {'filename': 'str'} }
> diff --git a/qmp-commands.hx b/qmp-commands.hx
> index ed3ab92..b796be5 100644
> --- a/qmp-commands.hx
> +++ b/qmp-commands.hx
> @@ -586,6 +586,33 @@ Example:
>  EQMP
>  
>      {
> +        .name       = "xen-load-devices-state",
> +        .args_type  = "filename:F",
> +        .mhandler.cmd_new = qmp_marshal_input_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_input_xen_set_global_dirty_log,
> diff --git a/savevm.c b/savevm.c
> index 22123be..3ebc01f 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -41,6 +41,7 @@
>  #include "qemu/iov.h"
>  #include "block/snapshot.h"
>  #include "block/qapi.h"
> +#include "hw/xen/xen.h"
>  
>  #define SELF_ANNOUNCE_ROUNDS 5
>  
> @@ -802,6 +803,14 @@ int qemu_loadvm_state(QEMUFile *f)
>                  goto out;
>              }
>  
> +            /* Validate if it is a device's state */
> +            if (xen_enabled() && se->is_ram) {
> +                fprintf(stderr, "loadvm: %s RAM loading not allowed on 
> Xen\n",
> +                        idstr);
> +                ret = -EINVAL;
> +                goto out;
> +            }
> +
>              /* Add entry */
>              le = g_malloc0(sizeof(*le));
>  
> @@ -1027,6 +1036,33 @@ 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 saved_vm_running;
> +    int ret;
> +
> +    saved_vm_running = runstate_is_running();
> +    vm_stop(RUN_STATE_RESTORE_VM);
> +
> +    f = qemu_fopen(filename, "rb");
> +    if (!f) {
> +        error_setg_file_open(errp, errno, filename);
> +        goto out;
> +    }
> +
> +    ret = qemu_loadvm_state(f);
> +    qemu_fclose(f);
> +    if (ret < 0) {
> +        error_set(errp, QERR_IO_ERROR);
> +    }
> +
> +out:
> +    if (saved_vm_running) {
> +        vm_start();
> +    }
> +}
> +
>  int load_vmstate(const char *name)
>  {
>      BlockDriverState *bs, *bs_vm_state;
> -- 
> 1.9.3
> 
> 

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