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

[zhanghailiang <zhang.zhanghailiang@huawei.com>]

On 2015/7/4 2:03, Dr. David Alan Gilbert wrote:
> * 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

Yes, it will break migration if the QEMU in destination and source not enable/disable (configure) this
feature together, also not compatible with old version on migration.

> 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.
>

Hmm, his method can address the above problems, (though, we will still fail when we configure
with --enable-colo in source side and --disable-colo in destination, but that is what
we want, we should not go into colo mode if secondary host is not enable this feature).
I will look into his patch, and fix that in next version, thanks,

zhanghailiang

> 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
>
> .
>