[Xen-changelog] [qemu-xen master] migration: Fix return code of ram_save_iterate()

[patchbot@xxxxxxx]

commit 5c90308f07335451a08c030dc40a9eed4698152b
Author:     Thomas Huth <thuth@xxxxxxxxxx>
AuthorDate: Fri Nov 4 14:10:17 2016 +0100
Commit:     Juan Quintela <quintela@xxxxxxxxxx>
CommitDate: Mon Nov 14 19:35:41 2016 +0100

    migration: Fix return code of ram_save_iterate()
    
    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@xxxxxxxxxx>
    Reviewed-by: Juan Quintela <quintela@xxxxxxxxxx>
    Signed-off-by: Juan Quintela <quintela@xxxxxxxxxx>
---
 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 */
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#master

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