From: Dr. David Alan Gilbert Date: Thu, 10 Dec 2015 16:31:46 +0000 (+0000) Subject: Fix xbzrle vs last_sent_block update X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=3fd3c4b37c116cce7e9810fcc15a0a2cf15115a5;p=qemu.git 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 Reviewed-by: Juan Quintela Message-id: 1449765106-6528-1-git-send-email-dgilbert@redhat.com Signed-off-by: Peter Maydell --- diff --git a/migration/ram.c b/migration/ram.c index 1eb155aedd..0490f005dd 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;