Migration pull 2021-07-13

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Merge remote-tracking branch 'remotes/dgilbert-gitlab/tags/pull-migration-20210713a' into staging

Migration pull 2021-07-13

# gpg: Signature made Tue 13 Jul 2021 16:22:28 BST
# gpg:                using RSA key 45F5C71B4A0CB7FB977A9FA90516331EBC5BFDE7
# gpg: Good signature from "Dr. David Alan Gilbert (RH2) <dgilbert@redhat.com>" [full]
# Primary key fingerprint: 45F5 C71B 4A0C B7FB 977A  9FA9 0516 331E BC5B FDE7

* remotes/dgilbert-gitlab/tags/pull-migration-20210713a:
  migration: Move bitmap_mutex out of migration_bitmap_clear_dirty()
  migration: Clear error at entry of migrate_fd_connect()
  migration: Don't do migrate cleanup if during postcopy resume
  migration: Release return path early for paused postcopy
  migration: failover: emit a warning when the card is not fully unplugged
  migration/rdma: prevent from double free the same mr

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

migration/migration.c

@@ -1855,6 +1855,15 @@ void migrate_set_error(MigrationState *s, const Error *error)
     }
 }
 
+static void migrate_error_free(MigrationState *s)
+{
+    QEMU_LOCK_GUARD(&s->error_mutex);
+    if (s->error) {
+        error_free(s->error);
+        s->error = NULL;
+    }
+}
+
 void migrate_fd_error(MigrationState *s, const Error *error)
 {
     trace_migrate_fd_error(error_get_pretty(error));
@@ -2818,12 +2827,12 @@ out:
              * Maybe there is something we can do: it looks like a
              * network down issue, and we pause for a recovery.
              */
+            qemu_fclose(rp);
+            ms->rp_state.from_dst_file = NULL;
+            rp = NULL;
             if (postcopy_pause_return_path_thread(ms)) {
                 /* Reload rp, reset the rest */
-                if (rp != ms->rp_state.from_dst_file) {
+                rp = ms->rp_state.from_dst_file;
-                    qemu_fclose(rp);
-                    rp = ms->rp_state.from_dst_file;
-                }
                 ms->rp_state.error = false;
                 goto retry;
             }
@@ -3701,6 +3710,10 @@ static void qemu_savevm_wait_unplug(MigrationState *s, int old_state,
             while (timeout-- && qemu_savevm_state_guest_unplug_pending()) {
                 qemu_sem_timedwait(&s->wait_unplug_sem, 250);
             }
+            if (qemu_savevm_state_guest_unplug_pending()) {
+                warn_report("migration: partially unplugged device on "
+                            "failure");
+            }
         }
 
         migrate_set_state(&s->state, MIGRATION_STATUS_WAIT_UNPLUG, new_state);
@@ -3966,6 +3979,13 @@ void migrate_fd_connect(MigrationState *s, Error *error_in)
     int64_t rate_limit;
     bool resume = s->state == MIGRATION_STATUS_POSTCOPY_PAUSED;
 
+    /*
+     * If there's a previous error, free it and prepare for another one.
+     * Meanwhile if migration completes successfully, there won't have an error
+     * dumped when calling migrate_fd_cleanup().
+     */
+    migrate_error_free(s);
+
     s->expected_downtime = s->parameters.downtime_limit;
     if (resume) {
         assert(s->cleanup_bh);
@@ -3975,7 +3995,18 @@ void migrate_fd_connect(MigrationState *s, Error *error_in)
     }
     if (error_in) {
         migrate_fd_error(s, error_in);
-        migrate_fd_cleanup(s);
+        if (resume) {
+            /*
+             * Don't do cleanup for resume if channel is invalid, but only dump
+             * the error.  We wait for another channel connect from the user.
+             * The error_report still gives HMP user a hint on what failed.
+             * It's normally done in migrate_fd_cleanup(), but call it here
+             * explicitly.
+             */
+            error_report_err(error_copy(s->error));
+        } else {
+            migrate_fd_cleanup(s);
+        }
         return;
     }
 

migration/ram.c

@@ -795,8 +795,6 @@ static inline bool migration_bitmap_clear_dirty(RAMState *rs,
 {
     bool ret;
 
-    QEMU_LOCK_GUARD(&rs->bitmap_mutex);
-
     /*
      * Clear dirty bitmap if needed.  This _must_ be called before we
      * send any of the page in the chunk because we need to make sure
@@ -2834,6 +2832,14 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
         goto out;
     }
 
+    /*
+     * We'll take this lock a little bit long, but it's okay for two reasons.
+     * Firstly, the only possible other thread to take it is who calls
+     * qemu_guest_free_page_hint(), which should be rare; secondly, see
+     * MAX_WAIT (if curious, further see commit 4508bd9ed8053ce) below, which
+     * guarantees that we'll at least released it in a regular basis.
+     */
+    qemu_mutex_lock(&rs->bitmap_mutex);
     WITH_RCU_READ_LOCK_GUARD() {
         if (ram_list.version != rs->last_version) {
             ram_state_reset(rs);
@@ -2893,6 +2899,7 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
             i++;
         }
     }
+    qemu_mutex_unlock(&rs->bitmap_mutex);
 
     /*
      * Must occur before EOS (or any QEMUFile operation)
@@ -3682,6 +3689,7 @@ void colo_flush_ram_cache(void)
     unsigned long offset = 0;
 
     memory_global_dirty_log_sync();
+    qemu_mutex_lock(&ram_state->bitmap_mutex);
     WITH_RCU_READ_LOCK_GUARD() {
         RAMBLOCK_FOREACH_NOT_IGNORED(block) {
             ramblock_sync_dirty_bitmap(ram_state, block);
@@ -3710,6 +3718,7 @@ void colo_flush_ram_cache(void)
         }
     }
     trace_colo_flush_ram_cache_end();
+    qemu_mutex_unlock(&ram_state->bitmap_mutex);
 }
 
 /**

migration/rdma.c

@@ -1143,6 +1143,7 @@ static int qemu_rdma_reg_whole_ram_blocks(RDMAContext *rdma)
 
     for (i--; i >= 0; i--) {
         ibv_dereg_mr(local->block[i].mr);
+        local->block[i].mr = NULL;
         rdma->total_registrations--;
     }