On 03/31/2012 11:12 PM, Takuya Yoshikawa wrote: > This is what I wanted to read before starting GET_DIRTY_LOG work: about > possible race between VCPU threads and GET_DIRTY_LOG thread. > > Although most things look trivial, there seem to be some interesting assumptions > the correctness is based on including mmu lock usage. > > Takuya > > === > 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? -- 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
