On 08/01/2012 06:07 PM, Nadav Har'El wrote: > On Wed, Aug 01, 2012, Avi Kivity wrote about "Re: Nested kvm_intel broken on pre 3.3 hosts": >> Right - it's not just kvm-as-a-guest that will trip on this. But >> there's no point in everyone backporting it on their own. If you're >> doing the backport, please post it here and we'll forward it to the >> stable branch. > > If I understand correctly, the failure occurs because new versions of > KVM refuse to work if the processor doesn't support CPU_BASED_RDPMC_EXITING - > which older versions of nested VMX didn't say that they did. Right. > But must the KVM guest refuse to work if this feature isn't supported? > I.e., why not move in setup_vmcs_config() the CPU_BASED_RDPMC_EXITING > from "min" to "opt"? Isn't losing the PMU feature a lesser evil than > not working at all? In any case, perhaps the original reporter can use > this as a workaround, at least, because it requires modifying the (L1) > guest, not the host. Real processors that don't support RDPMC exiting don't exist (and logically cannot exist unless they also drop support for the RDPMC instruction). Given it's a clear host bug I'd rather fix it than making the guest more complicated, even by a small amount. The hypervisor needs to be updated on a regular schedule anyway, so there's no risk of locking users out for more than a short while. -- error compiling committee.c: too many arguments to function -- 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
