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

[Steven Sistare]

On 7/17/2024 2:39 PM, Fabiano Rosas wrote:

Steve Sistare <steven.sist...@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.sist...@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;