Re: [RFC PATCH 04/17] COLO info: use colo info to tell migration target colo is enabled

[Hongyang Yang <yanghy@cn.fujitsu.com>]

在 08/01/2014 10:43 PM, Dr. David Alan Gilbert 写道:
> * Yang Hongyang (yanghy@cn.fujitsu.com) wrote:
>> migrate colo info to migration target to tell the target colo is
>> enabled.
>
> If I understand this correctly this means that you send a 'colo info' device
> information for migrations that don't have COLO enabled; that's bad because
> it breaks migration unless the destination has it; I guess it's OK if you
> were to guard it with a thing so it didn't do it for old machine-types.
>
> You could use the QEMU_VM_COMMAND sections I've created for postcopy;
> ( http://lists.gnu.org/archive/html/qemu-devel/2014-07/msg00889.html ) and
> add a QEMU_VM_CMD_COLO to indicate you want the destination to become an SVM,
>    then check the capability near the start of migration and send the command.

Thank you for the reference, I've read part of your Postcopy patches, but
haven't into detailed implementation. I will use QEMUSizedBuffer/QEMUFile in
next version. For QEMU_VM_COMMAND sections, can you separate it out so that I
can make use of it? Do you have a public git tree or something?

>
> Or perhaps there's a way to add the colo-info device on the command line so it's
> not always there.
>
> Dave
>
>> Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
>> ---
>>   Makefile.objs                      |  1 +
>>   include/migration/migration-colo.h |  3 ++
>>   migration-colo-comm.c              | 68 ++++++++++++++++++++++++++++++++++++++
>>   vl.c                               |  4 +++
>>   4 files changed, 76 insertions(+)
>>   create mode 100644 migration-colo-comm.c
>>
>> diff --git a/Makefile.objs b/Makefile.objs
>> index cab5824..1836a68 100644
>> --- a/Makefile.objs
>> +++ b/Makefile.objs
>> @@ -50,6 +50,7 @@ common-obj-$(CONFIG_POSIX) += os-posix.o
>>   common-obj-$(CONFIG_LINUX) += fsdev/
>>
>>   common-obj-y += migration.o migration-tcp.o
>> +common-obj-y += migration-colo-comm.o
>>   common-obj-$(CONFIG_COLO) += migration-colo.o
>>   common-obj-y += vmstate.o
>>   common-obj-y += qemu-file.o
>> diff --git a/include/migration/migration-colo.h b/include/migration/migration-colo.h
>> index 35b384c..e3735d8 100644
>> --- a/include/migration/migration-colo.h
>> +++ b/include/migration/migration-colo.h
>> @@ -12,6 +12,9 @@
>>   #define QEMU_MIGRATION_COLO_H
>>
>>   #include "qemu-common.h"
>> +#include "migration/migration.h"
>> +
>> +void colo_info_mig_init(void);
>>
>>   bool colo_supported(void);
>>
>> diff --git a/migration-colo-comm.c b/migration-colo-comm.c
>> new file mode 100644
>> index 0000000..ccbc246
>> --- /dev/null
>> +++ b/migration-colo-comm.c
>> @@ -0,0 +1,68 @@
>> +/*
>> + *  COarse-grain LOck-stepping Virtual Machines for Non-stop Service (COLO)
>> + *  (a.k.a. Fault Tolerance or Continuous Replication)
>> + *
>> + *  Copyright (C) 2014 FUJITSU LIMITED
>> + *
>> + * 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>
>> +
>> +#define DEBUG_COLO
>> +
>> +#ifdef DEBUG_COLO
>> +#define DPRINTF(fmt, ...) \
>> +    do { fprintf(stdout, "COLO: " fmt, ## __VA_ARGS__); } while (0)
>> +#else
>> +#define DPRINTF(fmt, ...) \
>> +    do { } while (0)
>> +#endif
>> +
>> +static bool colo_requested;
>> +
>> +/* save */
>> +
>> +static bool migrate_use_colo(void)
>> +{
>> +    MigrationState *s = migrate_get_current();
>> +    return s->enabled_capabilities[MIGRATION_CAPABILITY_COLO];
>> +}
>> +
>> +static void colo_info_save(QEMUFile *f, void *opaque)
>> +{
>> +    qemu_put_byte(f, migrate_use_colo());
>> +}
>> +
>> +/* restore */
>> +
>> +static int colo_info_load(QEMUFile *f, void *opaque, int version_id)
>> +{
>> +    int value = qemu_get_byte(f);
>> +
>> +    if (value && !colo_supported()) {
>> +        fprintf(stderr, "COLO is not supported\n");
>> +        return -EINVAL;
>> +    }
>> +
>> +    if (value && !colo_requested) {
>> +        DPRINTF("COLO requested!\n");
>> +    }
>> +
>> +    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 info", -1, 1,
>> +                         &savevm_colo_info_handlers, NULL);
>> +}
>> diff --git a/vl.c b/vl.c
>> index fe451aa..1a282d8 100644
>> --- a/vl.c
>> +++ b/vl.c
>> @@ -89,6 +89,7 @@ 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"
>> @@ -4339,6 +4340,9 @@ int main(int argc, char **argv, char **envp)
>>
>>       blk_mig_init();
>>       ram_mig_init();
>> +    if (colo_supported()) {
>> +        colo_info_mig_init();
>> +    }
>>
>>       /* open the virtual block devices */
>>       if (snapshot)
>> --
>> 1.9.1
>>
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
> .
>

-- 
Thanks,
Yang.