[PATCH v2 49/51] migration: Split save_live_pending() into state_pending_*

[Juan Quintela <quintela@redhat.com>]

We split the function into to:

- state_pending_estimate: We estimate the remaining state size without
  stopping the machine.

- state pending_exact: We calculate the exact amount of remaining
  state.

The only "device" that implements different functions for _estimate()
and _exact() is ram.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 docs/devel/migration.rst       | 18 ++++++++++--------
 docs/devel/vfio-migration.rst  |  4 ++--
 include/migration/register.h   | 12 ++++++++----
 migration/savevm.h             |  8 ++++++--
 hw/s390x/s390-stattrib.c       |  7 ++++---
 hw/vfio/migration.c            |  9 +++++----
 migration/block-dirty-bitmap.c | 11 ++++++-----
 migration/block.c              | 11 ++++++-----
 migration/migration.c          | 13 +++++++++----
 migration/ram.c                | 31 ++++++++++++++++++++++++-------
 migration/savevm.c             | 34 +++++++++++++++++++++++++++++-----
 hw/vfio/trace-events           |  2 +-
 migration/trace-events         |  7 ++++---
 13 files changed, 114 insertions(+), 53 deletions(-)

diff --git a/docs/devel/migration.rst b/docs/devel/migration.rst
index 3e9656d8e0..6f65c23b47 100644
--- a/docs/devel/migration.rst
+++ b/docs/devel/migration.rst
@@ -482,15 +482,17 @@ An iterative device must provide:
   - A ``load_setup`` function that initialises the data structures on the
     destination.
 
-  - A ``save_live_pending`` function that is called repeatedly and must
-    indicate how much more data the iterative data must save.  The core
-    migration code will use this to determine when to pause the CPUs
-    and complete the migration.
+  - A ``state_pending_exact`` function that indicates how much more
+    data we must save.  The core migration code will use this to
+    determine when to pause the CPUs and complete the migration.
 
-  - A ``save_live_iterate`` function (called after ``save_live_pending``
-    when there is significant data still to be sent).  It should send
-    a chunk of data until the point that stream bandwidth limits tell it
-    to stop.  Each call generates one section.
+  - A ``state_pending_estimate`` function that indicates how much more
+    data we must save.  When the estimated amount is smaller than the
+    threshold, we call ``state_pending_exact``.
+
+  - A ``save_live_iterate`` function should send a chunk of data until
+    the point that stream bandwidth limits tell it to stop.  Each call
+    generates one section.
 
   - A ``save_live_complete_precopy`` function that must transmit the
     last section for the device containing any remaining data.
diff --git a/docs/devel/vfio-migration.rst b/docs/devel/vfio-migration.rst
index 9ff6163c88..673057c90d 100644
--- a/docs/devel/vfio-migration.rst
+++ b/docs/devel/vfio-migration.rst
@@ -28,7 +28,7 @@ VFIO implements the device hooks for the iterative approach as follows:
 * A ``load_setup`` function that sets up the migration region on the
   destination and sets _RESUMING flag in the VFIO device state.
 
-* A ``save_live_pending`` function that reads pending_bytes from the vendor
+* A ``state_pending_exact`` function that reads pending_bytes from the vendor
   driver, which indicates the amount of data that the vendor driver has yet to
   save for the VFIO device.
 
@@ -114,7 +114,7 @@ Live migration save path
                     (RUNNING, _SETUP, _RUNNING|_SAVING)
                                   |
                     (RUNNING, _ACTIVE, _RUNNING|_SAVING)
-             If device is active, get pending_bytes by .save_live_pending()
+             If device is active, get pending_bytes by .state_pending_exact()
           If total pending_bytes >= threshold_size, call .save_live_iterate()
                   Data of VFIO device for pre-copy phase is copied
         Iterate till total pending bytes converge and are less than threshold
diff --git a/include/migration/register.h b/include/migration/register.h
index 5b5424ed8f..313b8e1c3b 100644
--- a/include/migration/register.h
+++ b/include/migration/register.h
@@ -46,9 +46,7 @@ typedef struct SaveVMHandlers {
 
     /* This runs outside the iothread lock!  */
     int (*save_setup)(QEMUFile *f, void *opaque);
-    void (*save_live_pending)(void *opaque,  uint64_t threshold_size,
-                              uint64_t *rest_precopy, uint64_t *rest_postcopy);
-    /* Note for save_live_pending:
+    /* Note for state_pending_*:
      * - res_precopy is for data which must be migrated in precopy
      *     phase or in stopped state, in other words - before target
      *     vm start
@@ -59,7 +57,13 @@ typedef struct SaveVMHandlers {
      * Sum of res_precopy and res_postcopy is the whole amount of
      * pending data.
      */
-
+    /* This calculate the exact remaining data to transfer */
+    void (*state_pending_exact)(void *opaque,  uint64_t threshold_size,
+                                uint64_t *rest_precopy, uint64_t *rest_postcopy);
+    /* This estimates the remaining data to transfer */
+    void (*state_pending_estimate)(void *opaque,  uint64_t threshold_size,
+                                   uint64_t *rest_precopy,
+                                   uint64_t *rest_postcopy);
 
     LoadStateHandler *load_state;
     int (*load_setup)(QEMUFile *f, void *opaque);
diff --git a/migration/savevm.h b/migration/savevm.h
index 98fae6f9b3..613f85e717 100644
--- a/migration/savevm.h
+++ b/migration/savevm.h
@@ -40,8 +40,12 @@ void qemu_savevm_state_cleanup(void);
 void qemu_savevm_state_complete_postcopy(QEMUFile *f);
 int qemu_savevm_state_complete_precopy(QEMUFile *f, bool iterable_only,
                                        bool inactivate_disks);
-void qemu_savevm_state_pending(uint64_t max_size,
-                               uint64_t *res_precopy, uint64_t *res_postcopy);
+void qemu_savevm_state_pending_exact(uint64_t max_size,
+                                     uint64_t *res_precopy,
+                                     uint64_t *res_postcopy);
+void qemu_savevm_state_pending_estimate(uint64_t max_size,
+                                        uint64_t *res_precopy,
+                                        uint64_t *res_postcopy);
 void qemu_savevm_send_ping(QEMUFile *f, uint32_t value);
 void qemu_savevm_send_open_return_path(QEMUFile *f);
 int qemu_savevm_send_packaged(QEMUFile *f, const uint8_t *buf, size_t len);
diff --git a/hw/s390x/s390-stattrib.c b/hw/s390x/s390-stattrib.c
index 9b74eeadf3..dfb95eb20c 100644
--- a/hw/s390x/s390-stattrib.c
+++ b/hw/s390x/s390-stattrib.c
@@ -182,8 +182,8 @@ static int cmma_save_setup(QEMUFile *f, void *opaque)
     return 0;
 }
 
-static void cmma_save_pending(void *opaque, uint64_t max_size,
-                              uint64_t *res_precopy, uint64_t *res_postcopy)
+static void cmma_state_pending(void *opaque, uint64_t *res_precopy,
+                               uint64_t *res_postcopy)
 {
     S390StAttribState *sas = S390_STATTRIB(opaque);
     S390StAttribClass *sac = S390_STATTRIB_GET_CLASS(sas);
@@ -369,7 +369,8 @@ static SaveVMHandlers savevm_s390_stattrib_handlers = {
     .save_setup = cmma_save_setup,
     .save_live_iterate = cmma_save_iterate,
     .save_live_complete_precopy = cmma_save_complete,
-    .save_live_pending = cmma_save_pending,
+    .state_pending_exact = cmma_state_pending,
+    .state_pending_estimate = cmma_state_pending,
     .save_cleanup = cmma_save_cleanup,
     .load_state = cmma_load,
     .is_active = cmma_active,
diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index 8ae1bd31a8..1545498e11 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -456,8 +456,8 @@ static void vfio_save_cleanup(void *opaque)
     trace_vfio_save_cleanup(vbasedev->name);
 }
 
-static void vfio_save_pending(void *opaque,  uint64_t threshold_size,
-                              uint64_t *res_precopy, uint64_t *res_postcopy)
+static void vfio_state_pending(void *opaque,  uint64_t threshold_size,
+                               uint64_t *res_precopy, uint64_t *res_postcopy)
 {
     VFIODevice *vbasedev = opaque;
     VFIOMigration *migration = vbasedev->migration;
@@ -470,7 +470,7 @@ static void vfio_save_pending(void *opaque,  uint64_t threshold_size,
 
     *res_precopy += migration->pending_bytes;
 
-    trace_vfio_save_pending(vbasedev->name, *res_precopy, *res_postcopy);
+    trace_vfio_state_pending(vbasedev->name, *res_precopy, *res_postcopy);
 }
 
 static int vfio_save_iterate(QEMUFile *f, void *opaque)
@@ -681,7 +681,8 @@ static int vfio_load_state(QEMUFile *f, void *opaque, int version_id)
 static SaveVMHandlers savevm_vfio_handlers = {
     .save_setup = vfio_save_setup,
     .save_cleanup = vfio_save_cleanup,
-    .save_live_pending = vfio_save_pending,
+    .state_pending_exact = vfio_state_pending,
+    .state_pending_estimate = vfio_state_pending,
     .save_live_iterate = vfio_save_iterate,
     .save_live_complete_precopy = vfio_save_complete_precopy,
     .save_state = vfio_save_state,
diff --git a/migration/block-dirty-bitmap.c b/migration/block-dirty-bitmap.c
index a445bdc3c3..5b24007650 100644
--- a/migration/block-dirty-bitmap.c
+++ b/migration/block-dirty-bitmap.c
@@ -761,9 +761,9 @@ static int dirty_bitmap_save_complete(QEMUFile *f, void *opaque)
     return 0;
 }
 
-static void dirty_bitmap_save_pending(void *opaque, uint64_t max_size,
-                                      uint64_t *res_precopy, 
-                                      uint64_t *res_postcopy)
+static void dirty_bitmap_state_pending(void *opaque, uint64_t max_size,
+                                       uint64_t *res_precopy,
+                                       uint64_t *res_postcopy)
 {
     DBMSaveState *s = &((DBMState *)opaque)->save;
     SaveBitmapState *dbms;
@@ -781,7 +781,7 @@ static void dirty_bitmap_save_pending(void *opaque, uint64_t max_size,
 
     qemu_mutex_unlock_iothread();
 
-    trace_dirty_bitmap_save_pending(pending, max_size);
+    trace_dirty_bitmap_state_pending(pending);
 
     *res_postcopy += pending;
 }
@@ -1250,7 +1250,8 @@ static SaveVMHandlers savevm_dirty_bitmap_handlers = {
     .save_live_complete_postcopy = dirty_bitmap_save_complete,
     .save_live_complete_precopy = dirty_bitmap_save_complete,
     .has_postcopy = dirty_bitmap_has_postcopy,
-    .save_live_pending = dirty_bitmap_save_pending,
+    .state_pending_exact = dirty_bitmap_state_pending,
+    .state_pending_estimate = dirty_bitmap_state_pending,
     .save_live_iterate = dirty_bitmap_save_iterate,
     .is_active_iterate = dirty_bitmap_is_active_iterate,
     .load_state = dirty_bitmap_load,
diff --git a/migration/block.c b/migration/block.c
index 39ce4003c6..8e6ad1c468 100644
--- a/migration/block.c
+++ b/migration/block.c
@@ -862,9 +862,9 @@ static int block_save_complete(QEMUFile *f, void *opaque)
     return 0;
 }
 
-static void block_save_pending(void *opaque, uint64_t max_size,
-                               uint64_t *res_precopy,
-                               uint64_t *res_postcopy)
+static void block_state_pending(void *opaque, uint64_t max_size,
+                                uint64_t *res_precopy,
+                                uint64_t *res_postcopy)
 {
     /* Estimate pending number of bytes to send */
     uint64_t pending;
@@ -883,7 +883,7 @@ static void block_save_pending(void *opaque, uint64_t max_size,
         pending = BLK_MIG_BLOCK_SIZE;
     }
 
-    trace_migration_block_save_pending(pending);
+    trace_migration_block_state_pending(pending);
     /* We don't do postcopy */
     *res_precopy += pending;
 }
@@ -1018,7 +1018,8 @@ static SaveVMHandlers savevm_block_handlers = {
     .save_setup = block_save_setup,
     .save_live_iterate = block_save_iterate,
     .save_live_complete_precopy = block_save_complete,
-    .save_live_pending = block_save_pending,
+    .state_pending_exact = block_state_pending,
+    .state_pending_estimate = block_state_pending,
     .load_state = block_load,
     .save_cleanup = block_migration_cleanup,
     .is_active = block_is_active,
diff --git a/migration/migration.c b/migration/migration.c
index a75a281635..9e18c911db 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -3756,13 +3756,18 @@ typedef enum {
  */
 static MigIterateState migration_iteration_run(MigrationState *s)
 {
-    uint64_t pending_size, pend_pre, pend_post;
+    uint64_t pend_pre, pend_post;
     bool in_postcopy = s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE;
 
-    qemu_savevm_state_pending(s->threshold_size, &pend_pre, &pend_post);
-    pending_size = pend_pre + pend_post;
+    qemu_savevm_state_pending_estimate(s->threshold_size, &pend_pre, &pend_post);
+    uint64_t pending_size = pend_pre + pend_post;
+    trace_migrate_pending_estimate(pending_size, s->threshold_size, pend_pre, pend_post);
 
-    trace_migrate_pending(pending_size, s->threshold_size, pend_pre, pend_post);
+    if (pend_pre <= s->threshold_size) {
+        qemu_savevm_state_pending_exact(s->threshold_size, &pend_pre, &pend_post);
+        pending_size = pend_pre + pend_post;
+        trace_migrate_pending_exact(pending_size, s->threshold_size, pend_pre, pend_post);
+    }
 
     if (pending_size && pending_size >= s->threshold_size) {
         /* Still a significant amount to transfer */
diff --git a/migration/ram.c b/migration/ram.c
index 63cb6544e5..ad5a2eeadd 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3392,17 +3392,33 @@ static int ram_save_complete(QEMUFile *f, void *opaque)
     return 0;
 }
 
-static void ram_save_pending(void *opaque, uint64_t max_size,
-                             uint64_t *res_precopy, uint64_t *res_postcopy)
+static void ram_state_pending_estimate(void *opaque, uint64_t max_size,
+                                       uint64_t *res_precopy,
+                                       uint64_t *res_postcopy)
 {
     RAMState **temp = opaque;
     RAMState *rs = *temp;
-    uint64_t remaining_size;
 
-    remaining_size = rs->migration_dirty_pages * TARGET_PAGE_SIZE;
+    uint64_t remaining_size = rs->migration_dirty_pages * TARGET_PAGE_SIZE;
 
-    if (!migration_in_postcopy() &&
-        remaining_size < max_size) {
+    if (migrate_postcopy_ram()) {
+        /* We can do postcopy, and all the data is postcopiable */
+        *res_postcopy += remaining_size;
+    } else {
+        *res_precopy += remaining_size;
+    }
+}
+
+static void ram_state_pending_exact(void *opaque, uint64_t max_size,
+                                    uint64_t *res_precopy,
+                                    uint64_t *res_postcopy)
+{
+    RAMState **temp = opaque;
+    RAMState *rs = *temp;
+
+    uint64_t remaining_size = rs->migration_dirty_pages * TARGET_PAGE_SIZE;
+
+    if (!migration_in_postcopy()) {
         qemu_mutex_lock_iothread();
         WITH_RCU_READ_LOCK_GUARD() {
             migration_bitmap_sync_precopy(rs);
@@ -4558,7 +4574,8 @@ static SaveVMHandlers savevm_ram_handlers = {
     .save_live_complete_postcopy = ram_save_complete,
     .save_live_complete_precopy = ram_save_complete,
     .has_postcopy = ram_has_postcopy,
-    .save_live_pending = ram_save_pending,
+    .state_pending_exact = ram_state_pending_exact,
+    .state_pending_estimate = ram_state_pending_estimate,
     .load_state = ram_load,
     .save_cleanup = ram_save_cleanup,
     .load_setup = ram_load_setup,
diff --git a/migration/savevm.c b/migration/savevm.c
index 9ddcbba4e3..89b9075ff1 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1471,8 +1471,9 @@ flush:
  * the result is split into the amount for units that can and
  * for units that can't do postcopy.
  */
-void qemu_savevm_state_pending(uint64_t threshold_size, uint64_t *res_precopy,
-                               uint64_t *res_postcopy)
+void qemu_savevm_state_pending_exact(uint64_t threshold_size,
+                                     uint64_t *res_precopy,
+                                     uint64_t *res_postcopy)
 {
     SaveStateEntry *se;
 
@@ -1480,7 +1481,7 @@ void qemu_savevm_state_pending(uint64_t threshold_size, uint64_t *res_precopy,
     *res_postcopy = 0;
 
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
-        if (!se->ops || !se->ops->save_live_pending) {
+        if (!se->ops || !se->ops->state_pending_exact) {
             continue;
         }
         if (se->ops->is_active) {
@@ -1488,8 +1489,31 @@ void qemu_savevm_state_pending(uint64_t threshold_size, uint64_t *res_precopy,
                 continue;
             }
         }
-        se->ops->save_live_pending(se->opaque, threshold_size,
-                                   res_precopy, res_postcopy);
+        se->ops->state_pending_exact(se->opaque, threshold_size,
+                                     res_precopy, res_postcopy);
+    }
+}
+
+void qemu_savevm_state_pending_estimate(uint64_t threshold_size,
+                                        uint64_t *res_precopy,
+                                        uint64_t *res_postcopy)
+{
+    SaveStateEntry *se;
+
+    *res_precopy = 0;
+    *res_postcopy = 0;
+
+    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
+        if (!se->ops || !se->ops->state_pending_estimate) {
+            continue;
+        }
+        if (se->ops->is_active) {
+            if (!se->ops->is_active(se->opaque)) {
+                continue;
+            }
+        }
+        se->ops->state_pending_estimate(se->opaque, threshold_size,
+                                        res_precopy, res_postcopy);
     }
 }
 
diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
index a21cbd2a56..90a8aecb37 100644
--- a/hw/vfio/trace-events
+++ b/hw/vfio/trace-events
@@ -157,7 +157,7 @@ vfio_save_cleanup(const char *name) " (%s)"
 vfio_save_buffer(const char *name, uint64_t data_offset, uint64_t data_size, uint64_t pending) " (%s) Offset 0x%"PRIx64" size 0x%"PRIx64" pending 0x%"PRIx64
 vfio_update_pending(const char *name, uint64_t pending) " (%s) pending 0x%"PRIx64
 vfio_save_device_config_state(const char *name) " (%s)"
-vfio_save_pending(const char *name, uint64_t precopy, uint64_t postcopy) " (%s) precopy 0x%"PRIx64" postcopy 0x%"PRIx64
+vfio_state_pending(const char *name, uint64_t precopy, uint64_t postcopy) " (%s) precopy 0x%"PRIx64" postcopy 0x%"PRIx64
 vfio_save_iterate(const char *name, int data_size) " (%s) data_size %d"
 vfio_save_complete_precopy(const char *name) " (%s)"
 vfio_load_device_config_state(const char *name) " (%s)"
diff --git a/migration/trace-events b/migration/trace-events
index f2a873fd6c..84352f310a 100644
--- a/migration/trace-events
+++ b/migration/trace-events
@@ -150,7 +150,8 @@ migrate_fd_cleanup(void) ""
 migrate_fd_error(const char *error_desc) "error=%s"
 migrate_fd_cancel(void) ""
 migrate_handle_rp_req_pages(const char *rbname, size_t start, size_t len) "in %s at 0x%zx len 0x%zx"
-migrate_pending(uint64_t size, uint64_t max, uint64_t pre, uint64_t post) "pending size %" PRIu64 " max %" PRIu64 " (pre = %" PRIu64 " post=%" PRIu64 ")"
+migrate_pending_estimate(uint64_t size, uint64_t max, uint64_t pre, uint64_t post) "pending size %" PRIu64 " max %" PRIu64 " (pre = %" PRIu64 " post=%" PRIu64 ")"
+migrate_pending_exact(uint64_t size, uint64_t max, uint64_t pre, uint64_t post) "pending size %" PRIu64 " max %" PRIu64 " (pre = %" PRIu64 " post=%" PRIu64 ")"
 migrate_send_rp_message(int msg_type, uint16_t len) "%d: len %d"
 migrate_send_rp_recv_bitmap(char *name, int64_t size) "block '%s' size 0x%"PRIi64
 migration_completion_file_err(void) ""
@@ -330,7 +331,7 @@ send_bitmap_bits(uint32_t flags, uint64_t start_sector, uint32_t nr_sectors, uin
 dirty_bitmap_save_iterate(int in_postcopy) "in postcopy: %d"
 dirty_bitmap_save_complete_enter(void) ""
 dirty_bitmap_save_complete_finish(void) ""
-dirty_bitmap_save_pending(uint64_t pending, uint64_t max_size) "pending %" PRIu64 " max: %" PRIu64
+dirty_bitmap_state_pending(uint64_t pending) "pending %" PRIu64
 dirty_bitmap_load_complete(void) ""
 dirty_bitmap_load_bits_enter(uint64_t first_sector, uint32_t nr_sectors) "chunk: %" PRIu64 " %" PRIu32
 dirty_bitmap_load_bits_zeroes(void) ""
@@ -355,7 +356,7 @@ migration_block_save_device_dirty(int64_t sector) "Error reading sector %" PRId6
 migration_block_flush_blks(const char *action, int submitted, int read_done, int transferred) "%s submitted %d read_done %d transferred %d"
 migration_block_save(const char *mig_stage, int submitted, int transferred) "Enter save live %s submitted %d transferred %d"
 migration_block_save_complete(void) "Block migration completed"
-migration_block_save_pending(uint64_t pending) "Enter save live pending  %" PRIu64
+migration_block_state_pending(uint64_t pending) "Enter save live pending  %" PRIu64
 
 # page_cache.c
 migration_pagecache_init(int64_t max_num_items) "Setting cache buckets to %" PRId64
-- 
2.38.1