Glauber Costa wrote: > Gerd Hoffmann wrote: >> Jeremy Fitzhardinge wrote: >>> Xen could change the parameters in the instant after >>> get_time_values(). That change could be as a result of >>> suspend-resume, so the parameters >>> and the tsc could be wildly different. >> >> Ah, ok, forgot the rdtsc in the picture. With that in mind I fully >> agree that the loop is needed. I think kvm guests can even hit that one >> with the vcpu migrating to a different physical cpu, so we better handle >> it correctly ;) > > It's probably not needed for kvm, since we update everything everytime > we get scheduled in the host side, which would cover the case for > migration between physical cpus.
No, it wouldn't. The corner case we must catch is: guest reads time info, kvm reschedules the guest to another pcpu, guest reads the tsc. The time info used by the guest for the tsc delta is stale then, it belongs to the previous pcpu. cheers, Gerd -- http://kraxel.fedorapeople.org/xenner/ ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
