Re: [Qemu-devel] [PATCH COLO-Frame v6 03/31] COLO: migrate colo related info to slave

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

* zhanghailiang (zhang.zhanghailiang@huawei.com) wrote:
> We can know if VM in destination should go into COLO mode by refer to
> the info that has been migrated from PVM.
> 
> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
> Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> Signed-off-by: Gonglei <arei.gonglei@huawei.com>
> ---
>  include/migration/migration-colo.h |  2 ++
>  migration/Makefile.objs            |  1 +
>  migration/colo-comm.c              | 47 ++++++++++++++++++++++++++++++++++++++
>  trace-events                       |  3 +++
>  vl.c                               |  5 +++-
>  5 files changed, 57 insertions(+), 1 deletion(-)
>  create mode 100644 migration/colo-comm.c
> 
> diff --git a/include/migration/migration-colo.h b/include/migration/migration-colo.h
> index c6d0c51..e20a0c1 100644
> --- a/include/migration/migration-colo.h
> +++ b/include/migration/migration-colo.h
> @@ -14,7 +14,9 @@
>  #define QEMU_MIGRATION_COLO_H
>  
>  #include "qemu-common.h"
> +#include "migration/migration.h"
>  
>  bool colo_supported(void);
> +void colo_info_mig_init(void);
>  
>  #endif
> diff --git a/migration/Makefile.objs b/migration/Makefile.objs
> index 5a25d39..cb7bd30 100644
> --- a/migration/Makefile.objs
> +++ b/migration/Makefile.objs
> @@ -1,5 +1,6 @@
>  common-obj-y += migration.o tcp.o
>  common-obj-$(CONFIG_COLO) += colo.o
> +common-obj-y += colo-comm.o
>  common-obj-y += vmstate.o
>  common-obj-y += qemu-file.o qemu-file-buf.o qemu-file-unix.o qemu-file-stdio.o
>  common-obj-y += xbzrle.o
> diff --git a/migration/colo-comm.c b/migration/colo-comm.c
> new file mode 100644
> index 0000000..0b76eb4
> --- /dev/null
> +++ b/migration/colo-comm.c
> @@ -0,0 +1,47 @@
> +/*
> + * COarse-grain LOck-stepping Virtual Machines for Non-stop Service (COLO)
> + * (a.k.a. Fault Tolerance or Continuous Replication)
> + *
> + * Copyright (c) 2015 HUAWEI TECHNOLOGIES CO., LTD.
> + * Copyright (c) 2015 FUJITSU LIMITED
> + * Copyright (c) 2015 Intel Corporation
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or
> + * later. See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#include <migration/migration-colo.h>
> +#include "trace.h"
> +
> +static bool colo_requested;
> +
> +/* save */
> +static void colo_info_save(QEMUFile *f, void *opaque)
> +{
> +    qemu_put_byte(f, migrate_enable_colo());
> +}
> +
> +/* restore */
> +static int colo_info_load(QEMUFile *f, void *opaque, int version_id)
> +{
> +    int value = qemu_get_byte(f);
> +
> +    if (value && !colo_requested) {
> +        trace_colo_info_load("COLO request!");
> +    }
> +    colo_requested = value;
> +
> +    return 0;
> +}
> +
> +static SaveVMHandlers savevm_colo_info_handlers = {
> +    .save_state = colo_info_save,
> +    .load_state = colo_info_load,
> +};
> +
> +void colo_info_mig_init(void)
> +{
> +    register_savevm_live(NULL, "colo", -1, 1,
> +                         &savevm_colo_info_handlers, NULL);
> +}
> diff --git a/trace-events b/trace-events
> index 52b7efa..3f63019 100644
> --- a/trace-events
> +++ b/trace-events
> @@ -1466,6 +1466,9 @@ rdma_start_incoming_migration_after_rdma_listen(void) ""
>  rdma_start_outgoing_migration_after_rdma_connect(void) ""
>  rdma_start_outgoing_migration_after_rdma_source_init(void) ""
>  
> +# migration/colo-comm.c
> +colo_info_load(const char *msg) "%s"
> +
>  # kvm-all.c
>  kvm_ioctl(int type, void *arg) "type 0x%x, arg %p"
>  kvm_vm_ioctl(int type, void *arg) "type 0x%x, arg %p"
> diff --git a/vl.c b/vl.c
> index 2201e27..988567a 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -90,6 +90,7 @@ int main(int argc, char **argv)
>  #include "sysemu/dma.h"
>  #include "audio/audio.h"
>  #include "migration/migration.h"
> +#include "migration/migration-colo.h"
>  #include "sysemu/kvm.h"
>  #include "qapi/qmp/qjson.h"
>  #include "qemu/option.h"
> @@ -4261,7 +4262,9 @@ int main(int argc, char **argv, char **envp)
>  
>      blk_mig_init();
>      ram_mig_init();
> -
> +#ifdef CONFIG_COLO
> +    colo_info_mig_init();
> +#endif

Does't this still break migration compatibility?  I wouldn't
want to have to have two QEMU builds on a system, one built with COLO
and one built without COLO.   You need to arrange for the
section to only be sent if COLO is enabled (i.e. migrate_set_capability colo on).
One way to do that would be to use the new QEMU optional sections
that Juan added recently.

Dave

>      /* If the currently selected machine wishes to override the units-per-bus
>       * property of its default HBA interface type, do so now. */
>      if (machine_class->units_per_default_bus) {
> -- 
> 1.7.12.4
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK