On Apr 27, 2011, at 2:51 PM, Takuya Yoshikawa <yoshikawa.tak...@oss.ntt.co.jp> wrote:
> >>>> What kind of mmio should be traced here, device or CPU originated? Or both? >>>> >>>> Jan >>>> >>>> >>> >>> To let Kemari replay outputs upon failover, tracing CPU originated >>> mmio (specifically write requests) should be enough. >>> IIUC, we can reproduce device originated mmio as a result of cpu >>> originated mmio. >>> > > Sorry, but I don't understand why it is safe yet. > > The problem is not if the mmio's are to be replayed but if replaying > them will produce the same result, is it? No. That's the functionality of event-tap queuing. The mmio tap is for recording which CPU originated mmio resulted in I/O monitored at event-tap queuing. We expect the replayed result to be same as the primary, but we don't have to guarantee while it's queued. Thanks, Yoshi > > In other words, is it really idempotent? > > Takuya > >> >> OK, I see. >> >> But this tap will only work for KVM. I think you either have to catch >> the other paths that TCG could take as well or maybe better move the >> hook into kvm-all - then it's absolutely clear that this is no generic >> feature. >> >> Jan >>
