[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [xen-devel] System time monotonicity
> Although Xen is fine, guests can get confused if they're > relying on the > TSC. Fortunately, Windows doesn't rely on the TSC, and most folk run > Linux PV which also works fine. > > If you want to make Linux work HVM on such a system you need to either > convince it to not to use the TSC, or arrange for TSC reads to trap to > Xen and then compute the result based on Xen's time base. If you're > doing the latter, better hope that TSC reads aren't called > frequently... Hi Ian -- Let me clarify... unless my reading of the code is wrong, ALL hvm guests that rely on ANY (virtual) platform timer are UNKNOWINGLY relying on the physical TSCs. Thus if the underlying physical system has unsynchronized TSCs, different vcpus in an SMP HVM guest (or even the SAME vcpu when rescheduled on another pcpu) may find that consecutive reads of ANY (virtual) platform timer are unexpectedly non-monotonic, which violates the whole purpose of using a PLATFORM timer. I suspect this is unintended and bad? Thanks, Dan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
|
Lists.xenproject.org is hosted with RackSpace, monitoring our |