qemu_savevm_state_iterate() expects the iterators to return 1
when they are done, and 0 if there is still something left to do.
However, ram_save_iterate() does not obey this rule and returns
the number of saved pages instead. This causes a fatal hang with
ppc64 guests when you run QEMU like this (also works with TCG):
qemu-img create -f qcow2 /tmp/test.qcow2 1M
qemu-system-ppc64 -nographic -nodefaults -m 256 \
-hda /tmp/test.qcow2 -serial mon:stdio
... then switch to the monitor by pressing CTRL-a c and try to
save a snapshot with "savevm test1" for example.
After the first iteration, ram_save_iterate() always returns 0 here,
so that qemu_savevm_state_iterate() hangs in an endless loop and you
can only "kill -9" the QEMU process.
Fix it by using proper return values in ram_save_iterate().
Signed-off-by: Thomas Huth <th...@redhat.com>
---
migration/ram.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/migration/ram.c b/migration/ram.c
index fb9252d..a1c8089 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1987,7 +1987,7 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
int ret;
int i;
int64_t t0;
- int pages_sent = 0;
+ int done = 0;
rcu_read_lock();
if (ram_list.version != last_version) {
@@ -2007,9 +2007,9 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
pages = ram_find_and_save_block(f, false, &bytes_transferred);
/* no more pages to sent */
if (pages == 0) {
+ done = 1;
break;
}
- pages_sent += pages;
acct_info.iterations++;
/* we want to check in the 1st loop, just in case it was the 1st time
@@ -2044,7 +2044,7 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
return ret;
}
- return pages_sent;
+ return done;
}
/* Called with iothread lock */
--
1.8.3.1
