I found a bug in QEMU 2.12 with adding memory-backend while live migration
thread is running.
But it seems that this bug was implicitly fixed in this commit (QEMU 3.0):
b895de50: migration: discard non-migratable RAMBlocks
I think it's better to disallow add/del memory backends during migration to
to prevent other possible problems. Anyway, user can't use this memory because
of disabled hotplug/hotunplug devs.
The idea of this commit is the same as that:
b06424de: migration: Disable hotplug/unplug memory during migration
Backtrace of this bug in QEMU 2.12:
0 find_next_bit (addr=addr@entry=0x0, size=size@entry=262144,
offset=offset@entry=0) at util/bitops.c:46
1 migration_bitmap_find_dirty (rs=0x7f58f80008c0, start=0, rb=0x5557e66e3200)
at migration/ram.c:816
2 find_dirty_block (again=<synthetic pointer>, pss=<synthetic pointer>,
rs=0x7f58f80008c0) at migration/ram.c:1243
3 ram_find_and_save_block (rs=rs@entry=0x7f58f80008c0,
last_stage=last_stage@entry=false) at migration/ram.c:1592
4 ram_find_and_save_block (last_stage=false, rs=0x7f58f80008c0) at
migration/ram.c:2335
5 ram_save_iterate (f=0x5557e69f1000, opaque=<optimized out>) at
migration/ram.c:2338
6 qemu_savevm_state_iterate (f=0x5557e69f1000, postcopy=false) at
migration/savevm.c:1191
7 migration_iteration_run (s=0x5557e666b030) at migration/migration.c:2301
8 migration_thread (opaque=0x5557e666b030) at migration/migration.c:2409
9 start_thread (arg=0x7f59055d5700) at pthread_create.c:333
10 clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Signed-off-by: Yury Kotov <yury-ko...@yandex-team.ru>
---
backends/hostmem.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/backends/hostmem.c b/backends/hostmem.c
index f61093654e..5c71bd3f6b 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -18,6 +18,7 @@
#include "qapi/visitor.h"
#include "qemu/config-file.h"
#include "qom/object_interfaces.h"
+#include "migration/misc.h"
#ifdef CONFIG_NUMA
#include <numaif.h>
@@ -271,6 +272,11 @@ host_memory_backend_memory_complete(UserCreatable *uc,
Error **errp)
void *ptr;
uint64_t sz;
+ if (!migration_is_idle()) {
+ error_setg(errp, "Adding memory-backend isn't allowed while
migrating");
+ goto out;
+ }
+
if (bc->alloc) {
bc->alloc(backend, &local_err);
if (local_err) {
@@ -344,7 +350,8 @@ out:
static bool
host_memory_backend_can_be_deleted(UserCreatable *uc)
{
- if (host_memory_backend_is_mapped(MEMORY_BACKEND(uc))) {
+ if (host_memory_backend_is_mapped(MEMORY_BACKEND(uc)) ||
+ !migration_is_idle()) {
return false;
} else {
return true;
--
2.21.0
