Re: [Qemu-devel] [PATCH v6 1/1] Introduce "xen-load-devices-state"

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Stefano Stabellini (sstabellini@kernel.org) wrote:
> On Fri, 3 Jun 2016, Anthony PERARD wrote:
> > On Fri, Jun 03, 2016 at 05:58:34PM +0800, Changlong Xie wrote:
> > > From: Wen Congyang <wency@cn.fujitsu.com>
> > > 
> > > 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 <wency@cn.fujitsu.com>
> > > Signed-off-by: Changlong Xie <xiecl.fnst@cn.fujitsu.com>
> > 
> > Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
> 
> David,
> 
> can we still have your Ack on this patch?

Yes,

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>


Dave
> 
> 
> > > ---
> > >  migration/savevm.c | 37 +++++++++++++++++++++++++++++++++++++
> > >  qapi-schema.json   | 14 ++++++++++++++
> > >  qmp-commands.hx    | 27 +++++++++++++++++++++++++++
> > >  3 files changed, 78 insertions(+)
> > > 
> > > diff --git a/migration/savevm.c b/migration/savevm.c
> > > index 6c21231..ae2ef8b 100644
> > > --- a/migration/savevm.c
> > > +++ b/migration/savevm.c
> > > @@ -31,6 +31,7 @@
> > >  #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"
> > > @@ -1754,6 +1755,12 @@ 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));
> > >  
> > > @@ -2064,6 +2071,36 @@ void qmp_xen_save_devices_state(const char *filename, Error **errp)
> > >      }
> > >  }
> > >  
> > > +void qmp_xen_load_devices_state(const char *filename, Error **errp)
> > > +{
> > > +    QEMUFile *f;
> > > +    QIOChannelFile *ioc;
> > > +    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);
> > > +
> > > +    ioc = qio_channel_file_new_path(filename, O_RDONLY | O_BINARY, 0, errp);
> > > +    if (!ioc) {
> > > +        return;
> > > +    }
> > > +    f = qemu_fopen_channel_input(QIO_CHANNEL(ioc));
> > > +
> > > +    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 8483bdf..48c3a6f 100644
> > > --- a/qapi-schema.json
> > > +++ b/qapi-schema.json
> > > @@ -4201,6 +4201,20 @@
> > >    '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 28801a2..780e7f2 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
> > > 
> > > 
> > > 
> > 
> > -- 
> > Anthony PERARD
> > 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK