Re: [PATCH V2 03/11] migration: save cpr mode

[Steven Sistare]

On 7/17/2024 2:39 PM, Fabiano Rosas wrote:
> Steve Sistare <steven.sistare@oracle.com> writes:
>
> > Save the mode in CPR state, so the user does not need to explicitly specify
> > it for the target.  Modify migrate_mode() so it returns the incoming mode on
> > the target.
> >
> > Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> > ---
> >   include/migration/cpr.h |  7 +++++++
> >   migration/cpr.c         | 23 ++++++++++++++++++++++-
> >   migration/migration.c   |  1 +
> >   migration/options.c     |  9 +++++++--
> >   4 files changed, 37 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/migration/cpr.h b/include/migration/cpr.h
> > index 8e7e705..42b4019 100644
> > --- a/include/migration/cpr.h
> > +++ b/include/migration/cpr.h
> > @@ -8,6 +8,13 @@
> >   #ifndef MIGRATION_CPR_H
> >   #define MIGRATION_CPR_H
> >   
> > +#include "qapi/qapi-types-migration.h"
> > +
> > +#define MIG_MODE_NONE MIG_MODE__MAX
>
> What happens when a QEMU that knows about a new mode migrates into a
> QEMU that doesn't know that mode, i.e. sees it as MIG_MODE__MAX?
>
> I'd just use -1.

Good idea, thanks - steve

> > +
> > +MigMode cpr_get_incoming_mode(void);
> > +void cpr_set_incoming_mode(MigMode mode);
> > +
> >   typedef int (*cpr_walk_fd_cb)(int fd);
> >   void cpr_save_fd(const char *name, int id, int fd);
> >   void cpr_delete_fd(const char *name, int id);
> > diff --git a/migration/cpr.c b/migration/cpr.c
> > index 313e74e..1c296c6 100644
> > --- a/migration/cpr.c
> > +++ b/migration/cpr.c
> > @@ -21,10 +21,23 @@
> >   typedef QLIST_HEAD(CprFdList, CprFd) CprFdList;
> >   
> >   typedef struct CprState {
> > +    MigMode mode;
> >       CprFdList fds;
> >   } CprState;
> >   
> > -static CprState cpr_state;
> > +static CprState cpr_state = {
> > +    .mode = MIG_MODE_NONE,
> > +};
> > +
> > +MigMode cpr_get_incoming_mode(void)
> > +{
> > +    return cpr_state.mode;
> > +}
> > +
> > +void cpr_set_incoming_mode(MigMode mode)
> > +{
> > +    cpr_state.mode = mode;
> > +}
> >   
> >   /****************************************************************************/
> >   
> > @@ -124,11 +137,19 @@ void cpr_resave_fd(const char *name, int id, int fd)
> >   /*************************************************************************/
> >   #define CPR_STATE "CprState"
> >   
> > +static int cpr_state_presave(void *opaque)
> > +{
> > +    cpr_state.mode = migrate_mode();
> > +    return 0;
> > +}
> > +
> >   static const VMStateDescription vmstate_cpr_state = {
> >       .name = CPR_STATE,
> >       .version_id = 1,
> >       .minimum_version_id = 1,
> > +    .pre_save = cpr_state_presave,
> >       .fields = (VMStateField[]) {
> > +        VMSTATE_UINT32(mode, CprState),
> >           VMSTATE_QLIST_V(fds, CprState, 1, vmstate_cpr_fd, CprFd, next),
> >           VMSTATE_END_OF_LIST()
> >       }
> > diff --git a/migration/migration.c b/migration/migration.c
> > index e394ad7..0f47765 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -411,6 +411,7 @@ void migration_incoming_state_destroy(void)
> >           mis->postcopy_qemufile_dst = NULL;
> >       }
> >   
> > +    cpr_set_incoming_mode(MIG_MODE_NONE);
> >       yank_unregister_instance(MIGRATION_YANK_INSTANCE);
> >   }
> >   
> > diff --git a/migration/options.c b/migration/options.c
> > index 645f550..305397a 100644
> > --- a/migration/options.c
> > +++ b/migration/options.c
> > @@ -22,6 +22,7 @@
> >   #include "qapi/qmp/qnull.h"
> >   #include "sysemu/runstate.h"
> >   #include "migration/colo.h"
> > +#include "migration/cpr.h"
> >   #include "migration/misc.h"
> >   #include "migration.h"
> >   #include "migration-stats.h"
> > @@ -758,8 +759,12 @@ uint64_t migrate_max_postcopy_bandwidth(void)
> >   
> >   MigMode migrate_mode(void)
> >   {
> > -    MigrationState *s = migrate_get_current();
> > -    MigMode mode = s->parameters.mode;
> > +    MigMode mode = cpr_get_incoming_mode();
> > +
> > +    if (mode == MIG_MODE_NONE) {
> > +        MigrationState *s = migrate_get_current();
> > +        mode = s->parameters.mode;
> > +    }
> >   
> >       assert(mode >= 0 && mode < MIG_MODE__MAX);
> >       return mode;