Avi Kivity wrote: > On 11/17/2009 11:59 AM, Jan Kiszka wrote: >> Jan Kiszka wrote: >> >>> Dietmar Maurer wrote: >>> >>>> Hi Jan, >>>> >>>> The ubuntu code puts some barrier around the read. >>>> >>>> http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-hardy.git;a=commitdiff;h=198b348d96c9769153e72ca2461f8d841ddff1cc >>>> >>>> You simply override this with your own code - without barrier. Do you think this is correct? >>>> >>> Unless I messed it up again, I "overwrote" it with what is in latest >>> mainline regarding native_read_tsc. But I will check once more. >>> >> The removal of those barriers came with >> 0d12cdd5f883f508d33b85c1bae98fa28987c8c7 (sched: improve sched_clock() >> performance). So this is now an upstream question: >> >> Do we bother about the precision of native_read_tsc in svm or not? >> >> > > I doubt it matters. rdtsc will be followed by a return to the guest or > userspace, either of which is expensive enough to swamp any speculation. > Right. So the kvm-kmod replacement is also fine. Dietmar, if you could confirm that your issue is fixed, I would roll out a kvm-kmod-2.6.31.6b, likely the last version of this series. The .32 series will be updated on 2.6.32-final or the next KVM-affecting -rc release. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- 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
