On Wed, 2010-12-08 at 17:31 -0200, Marcelo Tosatti wrote: > On Tue, Dec 07, 2010 at 03:12:36PM -0200, Glauber Costa wrote: > > On Mon, 2010-12-06 at 19:04 -0200, Marcelo Tosatti wrote: > > > On Mon, Dec 06, 2010 at 09:03:46AM -0500, Glauber Costa wrote: > > > > Usually nobody usually thinks about that scenario (me included and specially), > > > > but kvmclock can be actually disabled in the host. > > > > > > > > It happens in two scenarios: > > > > 1. host too old. > > > > 2. we passed -kvmclock to our -cpu parameter. > > > > > > > > In both cases, we should not register kvmclock savevm section. This patch > > > > achives that by registering this section only if kvmclock is actually > > > > currently enabled in cpuid. > > > > > > > > The only caveat is that we have to register the savevm section a little bit > > > > later, since we won't know the final kvmclock state before cpuid gets parsed. > > > > > > What is the problem of registering the section? Restoring the value if > > > the host does not support it returns an error? > > > > > > Can't you ignore the error if kvmclock is not reported in cpuid, in the > > > restore handler? > > > > We can change the restore handler, but not the restore handler of > > binaries that are already out there. The motivation here is precisely to > > address migration to hosts without kvmclock, so it's better to have > > a way to disable, than to count on the fact that the other side will be > > able to ignore it. > > OK. Can't you register conditionally on kvmclock cpuid bit at the end of > kvm_arch_init_vcpu, in target-i386/kvm.c? Haven't looked at it, but will today. Actually, tsc has (obviously) the same problem and I plan to respin the patch today including a fix for it as well. Thanks! -- 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
