From b169059c8fbf15c3ffeec0f68b938cb9febd8db7 Mon Sep 17 00:00:00 2001
From: Peter Xu <peterx@redhat.com>
Date: Tue, 30 Nov 2021 16:00:28 +0800
Subject: [PATCH 5/6] memory: Fix incorrect calls of log_global_start/stop
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RH-Author: Peter Xu <peterx@redhat.com>
RH-MergeRequest: 77: memory: Fix qemu crash on continuous migrations of stopped VM
RH-Commit: [1/2] 6271ee689266b24d29d4c87f60e5b096ef5f5d63 (peterx/qemu-kvm)
RH-Bugzilla: 2044818
RH-Acked-by: Paolo Bonzini <None>
RH-Acked-by: David Hildenbrand <david@redhat.com>
RH-Acked-by: quintela1 <quintela@redhat.com>

We should only call the log_global_start/stop when the global dirty track
bitmask changes from zero<->non-zero.

No real issue reported for this yet probably because no immediate user to
enable both dirty rate measurement and migration at the same time.  However
it'll be good to be prepared for it.

Fixes: 63b41db4bc ("memory: make global_dirty_tracking a bitmask")
Cc: qemu-stable@nongnu.org
Cc: Hyman Huang <huangy81@chinatelecom.cn>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Juan Quintela <quintela@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Message-Id: <20211130080028.6474-1-peterx@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
(cherry picked from commit 7b0538ed3a22ce30817f818449d10701fb0821f9)
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 softmmu/memory.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/softmmu/memory.c b/softmmu/memory.c
index 7340e19ff5..81d4bf1454 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -2773,6 +2773,8 @@ static VMChangeStateEntry *vmstate_change;
 
 void memory_global_dirty_log_start(unsigned int flags)
 {
+    unsigned int old_flags = global_dirty_tracking;
+
     if (vmstate_change) {
         qemu_del_vm_change_state_handler(vmstate_change);
         vmstate_change = NULL;
@@ -2781,15 +2783,14 @@ void memory_global_dirty_log_start(unsigned int flags)
     assert(flags && !(flags & (~GLOBAL_DIRTY_MASK)));
     assert(!(global_dirty_tracking & flags));
     global_dirty_tracking |= flags;
-
     trace_global_dirty_changed(global_dirty_tracking);
 
-    MEMORY_LISTENER_CALL_GLOBAL(log_global_start, Forward);
-
-    /* Refresh DIRTY_MEMORY_MIGRATION bit.  */
-    memory_region_transaction_begin();
-    memory_region_update_pending = true;
-    memory_region_transaction_commit();
+    if (!old_flags) {
+        MEMORY_LISTENER_CALL_GLOBAL(log_global_start, Forward);
+        memory_region_transaction_begin();
+        memory_region_update_pending = true;
+        memory_region_transaction_commit();
+    }
 }
 
 static void memory_global_dirty_log_do_stop(unsigned int flags)
@@ -2800,12 +2801,12 @@ static void memory_global_dirty_log_do_stop(unsigned int flags)
 
     trace_global_dirty_changed(global_dirty_tracking);
 
-    /* Refresh DIRTY_MEMORY_MIGRATION bit.  */
-    memory_region_transaction_begin();
-    memory_region_update_pending = true;
-    memory_region_transaction_commit();
-
-    MEMORY_LISTENER_CALL_GLOBAL(log_global_stop, Reverse);
+    if (!global_dirty_tracking) {
+        memory_region_transaction_begin();
+        memory_region_update_pending = true;
+        memory_region_transaction_commit();
+        MEMORY_LISTENER_CALL_GLOBAL(log_global_stop, Reverse);
+    }
 }
 
 static void memory_vm_change_state_handler(void *opaque, bool running,
-- 
2.27.0