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migration: Fix return code of ram_save_iterate()

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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 <thuth@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Thomas Huth 2016-11-04 14:10:17 +01:00 committed by Juan Quintela
parent 8cc49f0302
commit 5c90308f07
1 changed files with 3 additions and 3 deletions
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6
migration/ram.c
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@ -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 */