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authorDr. David Alan Gilbert <dgilbert@redhat.com>2015-12-10 16:31:46 +0000
committerPeter Maydell <peter.maydell@linaro.org>2015-12-11 12:51:27 +0000
commit3fd3c4b37c116cce7e9810fcc15a0a2cf15115a5 (patch)
tree388fdaa41ba161791897718ed5c8a5688f682c07
parentb969526adf3d77c4a70d7aae41a2f6dccbd024a7 (diff)
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Fix xbzrle vs last_sent_block update
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 <dgilbert@redhat.com> Reviewed-by: Juan Quintela <quintela@redhat.com> Message-id: 1449765106-6528-1-git-send-email-dgilbert@redhat.com Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
-rw-r--r--migration/ram.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/migration/ram.c b/migration/ram.c
index 1eb155aed..0490f005d 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;