[PATCH qemu v3 4/4] savevm-async: restore run state from before snapshot

[Erik Fastermann <e.fastermann@proxmox.com>]

A snapshot of a paused VM left it in finish-migrate, where it stayed
until the VM was restarted. vm_needs_start only recorded whether the VM
had been running, so there was nothing to restore a paused VM to.

Store the run state instead and put it back, similar to
migration_iteration_finish().

Signed-off-by: Erik Fastermann <e.fastermann@proxmox.com>
---
 ...async-for-background-state-snapshots.patch | 63 ++++++++++++-------
 ...add-optional-buffer-size-to-QEMUFile.patch |  6 +-
 ...se-migration-blocker-check-for-snaps.patch |  4 +-
 3 files changed, 47 insertions(+), 26 deletions(-)

diff --git a/debian/patches/pve/0017-PVE-add-savevm-async-for-background-state-snapshots.patch b/debian/patches/pve/0017-PVE-add-savevm-async-for-background-state-snapshots.patch
index 30400a1..d7d5d0d 100644
--- a/debian/patches/pve/0017-PVE-add-savevm-async-for-background-state-snapshots.patch
+++ b/debian/patches/pve/0017-PVE-add-savevm-async-for-background-state-snapshots.patch
@@ -40,7 +40,8 @@ Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
 [EF: drop QIOChannel reference
      free migration vmdesc
      release resources on start failure path
-     include reason when file open fails]
+     include reason when file open fails
+     restore run state from before snapshot]
 Signed-off-by: Erik Fastermann <e.fastermann@proxmox.com>
 ---
  hmp-commands-info.hx         |  13 +
@@ -48,13 +49,13 @@ Signed-off-by: Erik Fastermann <e.fastermann@proxmox.com>
  include/migration/snapshot.h |   2 +
  include/monitor/hmp.h        |   3 +
  migration/meson.build        |   1 +
- migration/savevm-async.c     | 638 +++++++++++++++++++++++++++++++++++
- monitor/hmp-cmds.c           |  38 +++
+ migration/savevm-async.c     | 658 +++++++++++++++++++++++++++++++++++
+ monitor/hmp-cmds.c           |  38 ++
  qapi/migration.json          |  34 ++
  qapi/misc.json               |  25 ++
  qemu-options.hx              |  12 +
  system/vl.c                  |  10 +
- 11 files changed, 793 insertions(+)
+ 11 files changed, 813 insertions(+)
  create mode 100644 migration/savevm-async.c
 
 diff --git a/hmp-commands-info.hx b/hmp-commands-info.hx
@@ -152,10 +153,10 @@ index 0222d5ea6e..90d62d5723 100644
  ), gnutls, zlib)
 diff --git a/migration/savevm-async.c b/migration/savevm-async.c
 new file mode 100644
-index 0000000000..bf8509b261
+index 0000000000..0c8a10886f
 --- /dev/null
 +++ b/migration/savevm-async.c
-@@ -0,0 +1,638 @@
+@@ -0,0 +1,658 @@
 +#include "qemu/osdep.h"
 +#include "migration/channel-savevm-async.h"
 +#include "migration/migration.h"
@@ -210,7 +211,7 @@ index 0000000000..bf8509b261
 +    int state;
 +    Error *error;
 +    Error *blocker;
-+    bool vm_needs_start;
++    RunState vm_old_state;
 +    bool skip_vm_start;
 +    QEMUFile *file;
 +    int64_t total_time;
@@ -230,6 +231,24 @@ index 0000000000..bf8509b261
 +    return snap_state.state == SAVE_STATE_COMPLETED && snap_state.skip_vm_start;
 +}
 +
++static void restore_vm_old_state(void)
++{
++    RunState old_state = snap_state.vm_old_state;
++
++    if (old_state == RUN_STATE__MAX) {
++        return;
++    }
++    snap_state.vm_old_state = RUN_STATE__MAX;
++
++    if (runstate_is_live(old_state)) {
++        if (!should_skip_vm_start() && !runstate_check(RUN_STATE_SHUTDOWN)) {
++            vm_start();
++        }
++    } else if (runstate_check(RUN_STATE_FINISH_MIGRATE)) {
++        runstate_set(old_state);
++    }
++}
++
 +SaveVMInfo *qmp_query_savevm(Error **errp)
 +{
 +    SaveVMInfo *info = g_malloc0(sizeof(*info));
@@ -352,7 +371,7 @@ index 0000000000..bf8509b261
 +     */
 +    blk_set_aio_context(snap_state.target, qemu_get_aio_context(), NULL);
 +
-+    snap_state.vm_needs_start = runstate_is_running();
++    snap_state.vm_old_state = runstate_get();
 +    ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
 +    if (ret < 0) {
 +        save_snapshot_error("vm_stop_force_state error %d", ret);
@@ -396,12 +415,7 @@ index 0000000000..bf8509b261
 +        save_snapshot_error("process_savevm_cleanup: invalid state: %d",
 +                            snap_state.state);
 +    }
-+    if (snap_state.vm_needs_start) {
-+        if (!should_skip_vm_start()) {
-+            vm_start();
-+        }
-+        snap_state.vm_needs_start = false;
-+    }
++    restore_vm_old_state();
 +
 +    DPRINTF("timing: process_savevm_finalize (full) took %ld ms\n",
 +        qemu_clock_get_ms(QEMU_CLOCK_REALTIME) - start_time);
@@ -530,12 +544,18 @@ index 0000000000..bf8509b261
 +        return;
 +    }
 +
++    if (runstate_check(RUN_STATE_INMIGRATE)) {
++        error_setg(errp, "There's an incoming migration in progress");
++        return;
++    }
++
 +    /* initialize snapshot info */
 +    snap_state.bs_pos = 0;
 +    snap_state.total_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
 +    snap_state.blocker = NULL;
 +    snap_state.target_close_wait = (QemuCoSleep){ .to_wake = NULL };
 +    snap_state.skip_vm_start = has_skip_vm_start && skip_vm_start;
++    snap_state.vm_old_state = RUN_STATE__MAX;
 +
 +    if (snap_state.error) {
 +        error_free(snap_state.error);
@@ -543,7 +563,13 @@ index 0000000000..bf8509b261
 +    }
 +
 +    if (!statefile) {
-+        snap_state.vm_needs_start = runstate_is_running();
++        snap_state.vm_old_state = runstate_get();
++        /*
++         * vm_stop() only applies the run state if the VM is live, i.e. running
++         * or suspended. Otherwise the VM is already stopped and the run state
++         * is left alone, so restore_vm_old_state() has nothing to put back
++         * either.
++         */
 +        vm_stop(RUN_STATE_SAVE_VM);
 +        snap_state.state = SAVE_STATE_COMPLETED;
 +        return;
@@ -707,12 +733,7 @@ index 0000000000..bf8509b261
 +        return;
 +    }
 +
-+    if (snap_state.vm_needs_start) {
-+        if (!should_skip_vm_start()) {
-+            vm_start();
-+        }
-+        snap_state.vm_needs_start = false;
-+    }
++    restore_vm_old_state();
 +
 +    qemu_coroutine_enter(wait_for_close);
 +}
diff --git a/debian/patches/pve/0018-PVE-add-optional-buffer-size-to-QEMUFile.patch b/debian/patches/pve/0018-PVE-add-optional-buffer-size-to-QEMUFile.patch
index caea753..60bed8c 100644
--- a/debian/patches/pve/0018-PVE-add-optional-buffer-size-to-QEMUFile.patch
+++ b/debian/patches/pve/0018-PVE-add-optional-buffer-size-to-QEMUFile.patch
@@ -186,10 +186,10 @@ index a390554208..eda093b16a 100644
  
  G_DEFINE_AUTOPTR_CLEANUP_FUNC(QEMUFile, qemu_fclose)
 diff --git a/migration/savevm-async.c b/migration/savevm-async.c
-index bf8509b261..94849f5219 100644
+index 0c8a10886f..fd64c209ea 100644
 --- a/migration/savevm-async.c
 +++ b/migration/savevm-async.c
-@@ -426,7 +426,7 @@ void qmp_savevm_start(const char *statefile, bool has_skip_vm_start,
+@@ -451,7 +451,7 @@ void qmp_savevm_start(const char *statefile, bool has_skip_vm_start,
  
      QIOChannel *ioc = QIO_CHANNEL(qio_channel_savevm_async_new(snap_state.target,
                                                                 &snap_state.bs_pos));
@@ -198,7 +198,7 @@ index bf8509b261..94849f5219 100644
      object_unref(ioc);
  
      if (!snap_state.file) {
-@@ -593,7 +593,7 @@ int load_snapshot_from_blockdev(const char *filename, Error **errp)
+@@ -613,7 +613,7 @@ int load_snapshot_from_blockdev(const char *filename, Error **errp)
  
      /* restore the VM state */
      QIOChannel *ioc = QIO_CHANNEL(qio_channel_savevm_async_new(be, &bs_pos));
diff --git a/debian/patches/pve/0046-savevm-async-reuse-migration-blocker-check-for-snaps.patch b/debian/patches/pve/0046-savevm-async-reuse-migration-blocker-check-for-snaps.patch
index 153a569..5543423 100644
--- a/debian/patches/pve/0046-savevm-async-reuse-migration-blocker-check-for-snaps.patch
+++ b/debian/patches/pve/0046-savevm-async-reuse-migration-blocker-check-for-snaps.patch
@@ -136,10 +136,10 @@ index b6888daced..80eb0dcd1f 100644
  bool migration_in_postcopy(void);
  bool migration_postcopy_is_alive(MigrationStatus state);
 diff --git a/migration/savevm-async.c b/migration/savevm-async.c
-index 94849f5219..4ed5d510bf 100644
+index fd64c209ea..ae813c3d21 100644
 --- a/migration/savevm-async.c
 +++ b/migration/savevm-async.c
-@@ -391,7 +391,7 @@ void qmp_savevm_start(const char *statefile, bool has_skip_vm_start,
+@@ -416,7 +416,7 @@ void qmp_savevm_start(const char *statefile, bool has_skip_vm_start,
          return;
      }
  
-- 
2.47.3