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

[Hongyang Yang]

在 08/01/2014 10:43 PM, Dr. David Alan Gilbert 写道:
> * Yang Hongyang (address@hidden) 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 <address@hidden>
> > ---
> >   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 / address@hidden / Manchester, UK
> .

--
Thanks,
Yang.