On 07/30/2015 04:03 PM, Dr. David Alan Gilbert wrote: > * Dong, Eddie (eddie.d...@intel.com) wrote: >>>> A question here, the packet comparing may be very tricky. For example, >>>> some protocol use random data to generate unpredictable id or >>>> something else. One example is ipv6_select_ident() in Linux. So COLO >>>> needs a mechanism to make sure PVM and SVM can generate same random >>> data? >>> Good question, the random data connection is a big problem for COLO. At >>> present, it will trigger checkpoint processing because of the different >>> random >>> data. >>> I don't think any mechanisms can assure two different machines generate the >>> same random data. If you have any ideas, pls tell us :) >>> >>> Frequent checkpoint can handle this scenario, but maybe will cause the >>> performance poor. :( >>> >> The assumption is that, after VM checkpoint, SVM and PVM have identical >> internal state, so the pattern used to generate random data has high >> possibility to generate identical data at short time, at least... > They do diverge pretty quickly though; I have simple examples which > reliably cause a checkpoint because of simple randomness in applications. > > Dave >
And it will become even worse if hwrng is used in guest.
