On Sun, 01 Apr 2012 11:38:17 +0800 Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx> wrote: > > About MMU Page Fault Path: > > 1. Set bit in dirty bitmap > > 2. Make spte writable > > 3. Guest re-execute the write > > > > If GET_DIRTY_LOG is allowed to write protect the page between step 1 and 2, > > that page will be made writable again at step 2 and the write at step 3 will > > not be caught. Since the userspace can process that page before step 3, the > > written data may be lost. To avoid this mmu lock must be held correctly in > > both sides as the current implementation does. > > > > > Hmm, according to (*2), if we set the dirty bit after make spte writeable, > it should be safe without holding mmu-lock? > Yes, probably. But I just checked the current code. Not sure about your fast page fault path. 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
