[GIT PULL 2/8] dump: refuse dump-guest-memory while guest RAM is being migrated

["Marc-André Lureau" <marcandre.lureau@redhat.com>]

From: "Denis V. Lunev" <den@openvz.org>

dump-guest-memory reads all of guest RAM. The existing guard only rejects
the dump in RUN_STATE_INMIGRATE, i.e. the precopy load phase. On a
postcopy destination the guest already runs (RUN_STATE_RUNNING) while its
pages are pulled from the source on demand.

A non-detached dump reads that RAM on the main thread with the BQL held.
Touching a not-yet-received page blocks on the userfault, and because the
postcopy incoming path itself takes the BQL to install pages, the
transfer that would satisfy the fault cannot progress: the VM deadlocks.

Use migration_guest_ram_loading(), which also covers postcopy, so the
dump is refused for the whole time the destination is still receiving
guest RAM.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20260619101834.228432-3-den@openvz.org>
---
 dump/dump.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/dump/dump.c b/dump/dump.c
index eb2ee1c10df..7fa2d6f788c 100644
--- a/dump/dump.c
+++ b/dump/dump.c
@@ -30,6 +30,7 @@
 #include "qemu/main-loop.h"
 #include "hw/misc/vmcoreinfo.h"
 #include "migration/blocker.h"
+#include "migration/misc.h"
 #include "hw/core/cpu.h"
 #include "win_dump.h"
 #include "qemu/range.h"
@@ -2080,8 +2081,8 @@ void qmp_dump_guest_memory(bool paging, const char *protocol,
     bool detach_p = false;
     bool kdump_raw = false;
 
-    if (runstate_check(RUN_STATE_INMIGRATE)) {
-        error_setg(errp, "Dump not allowed during incoming migration.");
+    if (migration_guest_ram_loading()) {
+        error_setg(errp, "Dump not allowed during migration.");
         return;
     }
 

-- 
2.54.0