From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
My fix (84e7b80a) replaced the last_sent_block update that I'd
removed earlier; however it was too aggressive in the xbzrle case.
save_xbzrle_page might return '0' to mean that the page didn't
need sending since it was the same as the last sent version;
in this case we can't update 'last_sent_block' since we didn't
actually send it.
Symptom: 'Illegal RAM offset 1018000' as we try and send a page
to the wrong RAMBlock; potentially that could be a data
corruption if you were really unlucky.
Fixes: 84e7b80a05c0c44b90533c6cd2f1db5c932ccf77
Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
---
migration/ram.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/migration/ram.c b/migration/ram.c
index 1eb155a..0490f00 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -716,6 +716,9 @@ static int save_zero_page(QEMUFile *f, RAMBlock *block,
ram_addr_t offset,
* ram_save_page: Send the given page to the stream
*
* Returns: Number of pages written.
+ * < 0 - error
+ * >=0 - Number of pages written - this might legally be 0
+ * if xbzrle noticed the page was the same.
*
* @f: QEMUFile where to send the data
* @block: block that contains the page we want to send
@@ -1249,7 +1252,13 @@ static int ram_save_target_page(MigrationState *ms,
QEMUFile *f,
if (unsentmap) {
clear_bit(dirty_ram_abs >> TARGET_PAGE_BITS, unsentmap);
}
- last_sent_block = block;
+ /* Only update last_sent_block if a block was actually sent; xbzrle
+ * might have decided the page was identical so didn't bother writing
+ * to the stream.
+ */
+ if (res > 0) {
+ last_sent_block = block;
+ }
}
return res;
--
2.5.0
