Am 27.09.2010 21:00, Zachary Amsden wrote: > On 09/25/2010 11:54 PM, Jan Kiszka wrote: >> That only leaves us with the likely wrong unstable declaration of the >> TSC after resume. And that raises the question for me if KVM is actually >> that much smarter than the Linux kernel in detecting TSC jumps. If >> something is missing, can't we improve the kernel's detection mechanism >> which already has suspend/resume support? >> > > Linux must make the the conservative choice about TSC being declared > unstable; if it is possible that it has become unstable, it is > unstable. Unfortunately, this bodes not well for us, as most of the > finer points of accuracy depend on having a stable TSC. > > There's a bunch of places that declare TSC unstable, and where in the > suspend / resume cycle that happens would depend on your actual hardware. It's absolutely clear where this happens: kvm_arch_vcpu_load. And it seems to happen as the TSC is reset due to suspend-to-RAM. Again: Linux recovers from this and continues to use the TSC. KVM is more picky, so my question is if this is really required. 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
