On 29.02.2012, at 18:50, Scott Wood <scottwood@xxxxxxxxxxxxx> wrote: > On 02/28/2012 08:16 PM, Alexander Graf wrote: >> When we know that we're running inside of a KVM guest, we don't have to >> worry about synchronizing timebases between different CPUs, since the >> host already took care of that. >> >> This fixes CPU overcommit scenarios where vCPUs could hang forever trying >> to sync each other while not being scheduled. >> >> Reported-by: Stuart Yoder <B08248@xxxxxxxxxxxxx> >> Signed-off-by: Alexander Graf <agraf@xxxxxxx> > > This should apply to any hypervisor, not just KVM. Sure, but do you have a generic function to evaluate that? :) > On book3e, Power ISA > says timebase is read-only on virtualized implementations. My > understanding is that book3s is paravirt-only (guest state is not > considered an implementation of the Power ISA), and it says "Writing the > Time Base is privileged, and can be done only in hypervisor state". For PR non-PAPR KVM, we are non-paravirt, but ignore tb writes iirc. > > Which platforms are you seeing this on? If it's on Freescale chips, > U-Boot should be doing the sync and Linux should never do it, even in > the absence of a hypervisor. This is on e500mc. Alex > > -Scott > > -- > To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- 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
