On Mon, 19 Mar 2012 17:34:49 +0800 Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx> wrote: > The current code is under the protection of s-rcu: > IIRC, it always holds s-rcu when write guest page and set dirty bit, > that mean the dirty page is logged either in the old dirty_bitmap or in the > current memslot->dirty_bitmap. Yes? Yes. I just wanted to explain that getting clear dirty bitmap by GET_DIRTY_LOG does not mean there is no dirty page: it just means that there was nothing logged when we updated the bitmap in get_dirty_log(). We cannot know if anything happend between the bitmap update and result check in the userspace. So even when we get a clear bitmap, we need to stop the VCPU threads and then do GET_DIRTY_LOG once more for live migration. The important thing is that every bit set by mark_page_dirty() can be found at some time in the future, including the final GET_DIRTY_LOG. Takuya -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
